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I-5 over Skagit River Bridge
Mt. Vernon, Washington
Before Repair
THE
Collapsed Span
American Tobacco Trail Pedestrian Bridge over I-40
Durham, North Carolina
After Repair
Precast Concrete Post-Tensioned
Stress Ribbon Deck
Architect: Steven Grover & Associates
CONCRETE
BRIDGE
MAGAZINE
SPRING 2014
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CONTENTS
12
Features
Taking the Lead
6
Kiewit adapts to new delivery methods, new technologies,
and changing requirements to build bridges ranging from the
simple to the complex.
Zilwaukee Bridge
12
Bearing replacement need determined after 18 years of service.
Full-Span Precasting of Railway Bridges
16
Fairmount Line Bridges Rehabilitating Boston’s commuter rail line.
20
Satus Creek Bridge 24
Curved, tilted, precast concrete box girders key to replacement project.
Photo: Michigan Department of Transportation.
20
Montlake Triangle Pedestrian Bridge 28
Curved, post-tensioned structure links Seattle campus to
downtown.
Departments
Editorial2
Concrete Calendar
4
Perspective10
Photo: The Louis Berger Group Inc.
Aesthetics Commentary
31
Accelerated Bridge Construction
33
FHWA—The Long-Term Bridge Performance
Program36
24
State—Hawaii38
CCC—Rain Rocks Rock Shed
40
Authority—Illinois Tollway
44
Concrete Connections
46
Photo: Kiewit.
AASHTO LRFD—2014 Interim Changes Related to
Concrete Structures
48
Photo: Washington State Department of Transportation Visual Engineering Resource Group.
Advertisers Index
CABA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Helser Industries . . . . . . . . . . . . . . . . . . . . . . 5
PERI. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Creative Design Resolutions. . . . . . . . . . . . . 3
Hilman Rollers . . . . . . . . . . . . . . . . . . . . . . . 34
Pile Dynamics. . . . . . . . . . . . . . . . . . . . . . . . 25
D.S. Brown. . . . . . . . . . . . . Inside Back Cover
LARSA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Safway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
DSI/Dywidag Systems Intl.. . . . . . . . . . . . . 27
MMFX. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Williams Form Engineering Corp.. . . . . . . . 42
FIGG . . . . . . . . . . . . . . . . . Inside Front Cover
Parsons Brinkerhoff. . . . . . . . . . . Back Cover
Fyfe. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
PCI. . . . . . . . . . . . . . . . . . . . . . . . 5, 19, 41, 43
ASPIRE, Spring 2014 | 1
EDITORIAL
Thinking in the Future Tense
William Nickas, Editor-in-Chief
American Segmental Bridge Institute
Photo: PCI.
A
t two separate, transportation-related meetings
in 2013, engineers in attendance heard
addresses by futurists. I thought, “What an intriguing
career!” My mind began to speculate, “Do they really
predict the future? Can they help a person regarding a
career or personal decision? Do they have insight into
investing?”
Exploring the subject a little further, I found a
book by a well-respected futurist, the late Dr. Edward
B. Lindaman. Dr. Lindaman had an earlier, 22-yearlong career as director of program planning for the
design and manufacture of the Apollo spacecraft at
Rockwell International. In his book, Thinking in
the Future Tense, Lindaman wrote: “It used to be
that the future, like the weather, was something that
everybody talked about but that remained totally
beyond human control. Today, we not only dream
about the future, worry over it, save for it, and invest in
it; we also are consciously and unconsciously creating
our future. The future may be very different from
today. The future will be what we make of it. What a
revolutionary idea!”*
Futurists work beyond horizons of 20 or 30 years,
where it is a real challenge to imagine the future.
Working with futurists and through various leadership
exercises, organizations can avoid becoming stale and
complacent, thus creating an environment of growth
and creativity.
Often we map out a week, a month, or even a year’s
worth of goals and tasks. The longer the scope of the
plan, the more we need to build in contingencies.
Often, we evaluate more than one possible scenario
and the range of responses to each. This is preparation
for change and consciously creating the future.
The construction industry is constantly coping
with change and managing expectations—future
outcomes. Those who are not prepared, often suffer
very expensive consequences.
In my editorial in the Summer 2013 issue of
ASPIRE,™ “Do Not Let the Perfect Be the Enemy of
Good,” I proposed some thoughts about dealing with
planning and change in our industry.
Then, in the Fall 2013 issue, “You Better Have
Teamwork, or You Better Be Perfect,” I presented my
observations about the need to be a part of a wellfunctioning team that grows, tests concepts, evaluates
ideas, and delivers the best possible product.
So, the latest change for ASPIRE became obvious: An
extended FOCUS series starting in this issue of ASPIRE.
For too long, the pages of ASPIRE have overlooked
the bridge builder as an integral part of the team! Yes,
often project articles have included an author who
represented the contractor and much attention was
paid to ensure accurate reporting on the contractor
participants in each project. But, we have yet to feature
a contractor in these pages.
The Editorial Advisory Board and all the supporting
associations agreed to alternate the FOCUS series
between contractors and consultants. With this issue,
ASPIRE presents its first contractor company profile. I
hope you are as excited as I am about glimpsing inside
the minds of concrete bridge builders as they apply
new materials and create new techniques to build our
nation’s infrastructure and deliver the community
icons from high-performance concrete.
*Lindaman, Edward B. 1978. Thinking in the Future Tense
(pp. 15-16). Broadman Press, Nashville, TN. 192 pp.
Epoxy Interest Group
Expanded Shale Clay and Slate Institute
Portland Cement Association
Post-Tensioning Institute
Precast/Prestressed Concrete Institute
200 West Adams Street
Suite 2100 Chicago, IL 60606
Phone: 312-786-0300
Fax: 312-621-1114
www.pci.org
Editor-in-Chief
William Nickas • [email protected]
Managing Technical Editor
Dr. Henry G. Russell
Program Manager
Nancy Turner • [email protected]
Associate Editors
Emily B. Lorenz
Craig A. Shutt
Art Director
Paul Grigonis
Layout Design
Tressa A. Park
2 | ASPIRE, Spring 2014
Editorial Advisory Board
William Nickas, Precast/Prestressed Concrete Institute
William R. Cox, American Segmental Bridge Institute
Dr. David McDonald, Epoxy Interest Group
Dr. Henry G. Russell, Henry G. Russell Inc.
Cover
To build 554 bridges as part of Missouri’s “Safe & Sound”
Bridge Improvement Program, Kiewit teamed with
Traylor Bros. Inc. and United Contractors Inc. to build a
new bridge every 1.6 working days for 3.5 years. For more
information on Missouri’s “Safe & Sound” program, see
the state article featuring Missouri in the Spring 2013 issue
of ASPIRE.
Photo: Kiewit.
Phone: 312-786-0300
Fax: 312-621-1114
www.pci.org
Ad Sales
Jim Oestmann
Phone: (847) 838-0500 • Cell: (847) 924-5497
Fax: (847) 838-0555 • [email protected]
Reprints
Paul Grigonis • [email protected]
Publisher
Precast/Prestressed200
Concrete
Institute
West Adams
Street I Suite 2100 I Chicago, IL 60606-5230
Phone: 312-786-0300 I Fax: 312-621-1114 I www.pci.org
James G. Toscas, President
Postmaster: Send address changes to ASPIRE, 200 W. Adams St., Suite 2100,
Chicago, IL 60606. Standard postage paid at Chicago, IL, and additional mailing offices.
ASPIRE (Vol. 8, No. 2), ISSN 1935-2093 is published quarterly by the Precast/
Prestressed Concrete Institute.
Copyright 2014, Precast/Prestressed Concrete Institute.
If you have a project to be considered for ASPIRE, send information to ASPIRE
200 W. Adams St., Suite 2100 • Chicago, IL 60606
phone: (312) 786-0300 • www.aspirebridge.org
• e-mail: [email protected]
200 West Adams Street I Suite 2100 I Chicago, IL 60606-5230
CONTRIBUTING AUTHORS
Shri Bhide is the director of
BrIM product management for
Bentley Systems Inc. in
Sunrise, Fla. He is active in the
bridge committees of PCI, ACI,
PTI, and TRB, and is a
registered Structural and
Professional Engineer in
several states.
Barbara Day is the BrIM
Director for the Americas with
Bentley Systems. She formerly
worked with the North
Carolina Department of
Transportation and has been
with Bentley for 18 years. She
is a registered Professional
Engineer in the state of North
Carolina.
Hamid Ghasemi, PhD, is
the leader of the infrastructure
management team for the
Federal Highway
Administration Office of
Infrastructure Research and
Development at the
Turner-Fairbank Highway
Research Center in McLean, Va.
Myint Lwin was director of
the FHWA Office of Bridge
Technology in Washington,
D.C. He was responsible for the
National Highway Bridge
Program direction, policy,
and guidance.
Ali Maher, PhD, is a
professor and director of the
Center for Advanced
Infrastructure &
Transportation, a U.S.
Department of Transportationdesignated University
Transportation Center, at
Rutgers University in
Piscataway, N.J.
Jorge E. Pagán-Ortiz is
the director of the Federal
Highway Administration
Office of Infrastructure
Research and Development at
the Turner-Fairbank
Highway Research Center in
McLean, Va.
CONCRETE CALENDAR 2014/2015
For links to websites, email addresses, or telephone numbers for
these events, go to www.aspirebridge.org and select “EVENTS.”
April 14-15, 2014
ASBI 2014 Grouting
Certification Training
J. J. Pickle Research Campus
The Commons Center
Austin, Tex.
April 21-25, 2014
National Bridge Preservation
Partnership Conference
Renaissance Orlando at SeaWorld
Orlando, Fla.
April 24-27, 2014
PCI Committee Days and
Membership Conference
Hyatt Magnificent Mile
Chicago, Ill.
April 28, 2014
2014 National Accelerated
Bridge Construction Conference
Call for Papers
http://2014abc.fiu.edu/
May 4-6, 2014
PTI Annual Convention
Norfolk Waterside Marriott
Norfolk, Va.
June 8-12, 2014
International Bridge Conference
David L. Lawrence Convention Center
Pittsburgh, Pa.
June 22-26, 2014
2014 AASHTO Subcommittee on
Bridges and Structures Meeting
Hyatt Regency
Columbus, Ohio
October 27-28, 2014
ASBI 26th Annual Convention
Hartford Marriott Downtown
Hartford, Conn.
December 4-5, 2014
2014 National Accelerated
Bridge Construction Conference
Miami, Fla.
January 11-15, 2015
94th Annual Meeting
Transportation Research Board
Walter E. Washington
Convention Center
Washington, D.C.
February 2-6, 2015
World of Concrete 2015
Las Vegas Convention Center
Las Vegas, Nev.
April 15-20, 2015
ACI Spring Convention
Marriott Hotel and Kansas City
Convention Center
Kansas City, Mo.
November 8-12, 2015
ACI Fall Convention
Sheraton
Denver, Colo.
Nominations for 2014 PCI
Titans Now Being Accepted
September 6-9, 2014
PCI Annual Convention and
Exhibition and National Bridge
Conference
Gaylord National Resort and
Convention Center
National Harbor, Md.
PCI is continuing its Titans of the
Industry program in 2014. Up to ten
more Titans will be honored at the
2014 PCI Convention as we celebrate
our 60th anniversary. Nominations for
the 2014 Titan award are now open
and will be accepted until April 18,
2014. If you would like to nominate a
deserving person who qualifies, please
send your nomination to PCI President’s
Office, 200 West Adams St., Suite 2100,
Chicago, IL 60606-5230, or email it to
[email protected]
October 26-30, 2014
ACI Fall Convention
Hilton Washington
Washington, D.C.
For a list of qualification or more
information, visit http://www.pci.org/
About_PCI/PCI_Awards_Programs/ or
contact Rebecca Coleman at bcoleman@
pci.org.
When it comes to your next project …
Helser Industries has a one track mind !
For over 50 years Helser has engineered and manufactured precise custom steel forms to meet the unique
requirements of their customers. Helser’s expertise was utilized in the construction of the Las Vegas monorail.
The success of this high profile project was instrumental in Helser forms being specified for the monorail system
currently under construction in Sao Paulo Brazil.
Whether your project requires precise architectural detail,
structural elements or transportation application,
Helser Industries is on track to get it done right and get it done on time!
What:
When:
Where:
Phone: 312-786-0300
Fax: 312-621-1114
www.pci.org
1-503-692-6909
www.helser.com
PCI Committee Days and Membership Conference
April 24 – 27, 2014
Hyatt Magnificent Mile, Chicago, Illinois
Phone: 312-786-0300
Fax: 312-621-1114
www.pci.org
Phone: 312-786-0300
Fax: 312-621-1114
www.pci.org
Join PCI for this outstanding opportunity to network, share ideas and insight with fellow PCI
members, and provide input to the industry’s Body of Knowledge.
You don’t need to be on a committee to attend – all members are welcome!
Visit www.pci.org and select Committees Days and Membership Conference on the Calendar under
200 West Adams
StreetEvents
I Suite 2100 for
I Chicago,
IL 60606-5230
News
and
more
information, registration details, and the full schedule of events. We look
forward to seeing you in Chicago!
FOCUS
TAKING THE LEAD
Kiewit adapts to new delivery methods, new technologies,
and changing requirements to build bridges ranging from the simple to the complex
by Craig A. Shutt
When the state of Missouri Department
of Transportation (MoDOT) revamped its
entire highway bridge system in 2009,
it presented a Kiewit-led, joint-venture,
design-build team with a significant
challenge: replace 554 bridges in four
years while the state refurbished 248
existing bridges simultaneously. The team
not only met the goal but finished in
3½ years, completing one bridge every
1.6 working days. To accomplish that
feat meant adapting to new delivery
methods, creating detailed strategic
plans, and thinking in innovative ways.
Such capabilities help Kiewit adapt to
new challenges every day.
“In general, the more complex, difficult,
and technical the project is, the better we
compete for the business,” says Ralph
Salamie, project sponsor (a management
position) for Kiewit. “Certainly, we
compete and win our share of the
smaller, more traditional infrastructure
projects. But we’re very competitive for
the larger, more complex projects.”
Missouri’s $685-million, design-build Safe
& Sound Bridge Improvement Program
certainly fits that bill. The state’s initial
plan called for the winning bidder to
design, build, finance, and maintain
all 802 bridges for 25 years. But when
bids were considerably higher than
anticipated, MoDOT removed the
bridges that needed rehabilitation and
repackaged the remainder as one large
design-build project. Kiewit’s jointventure team built 63 of the 554 bridges
and managed subcontractors for the rest.
For more details, see the Spring 2013
issue of ASPIRE.™
More Delivery Methods
Such unusual delivery methods are
becoming more common, Salamie notes.
“We still do a lot of rip-and-read work,
but more is design-build, which gives us
the ability to control the process.” They’re
also seeing construction manager/general
contractor (CM/GC) work grow and have
been involved in several P3 (Public-Private
Partnerships), in which they team with,
or even act as, developers to arrange the
financing and long-term operations of a
project. “We have had to become more
engaged in the process of design, project
financing, and long-term operation and
maintenance of our alternative delivery
projects.”
The $1.2-billion San Francisco Oakland Bay
Bridge Skyway Segment was built by a joint
venture led by Kiewit. The 1.2-mile-long,
14-span, twin precast concrete segmental
bridges feature 452 precast concrete segments,
the largest weighing as much as 750 tons. All
Photos: Kiewit.
These new delivery approaches lead
owners to look beyond lowest-bid pricing
and more heavily weigh other factors.
Kiewit has capitalized on the innovative
opportunities of alternative delivery
projects to increase its win ratio, Salamie
says. “More owners want the ‘best value’
option, which includes cost but also looks
at benefits in maintenance and design
life.”
bidders take the same set of drawings
and work up an estimate,” he explains.
“We now have joint ownership of
the design with the designer, where
our team’s design can be the biggest
differentiator in our competitive bid. We
expect our construction team to have a
working knowledge of the design, and
take responsibility for both design and
construction.”
Evolutions in delivery methods are
changing Kiewit’s approach to projects,
notes Jim Thomsen, who served as
project manager for Kiewit’s contract
with the Missouri Safe & Sound Bridge
Improvement Program. “On designbuild projects, our construction team is
integrated with the design team to ensure
constructability and operational efficiency.
Design risks and quantity growth are
identified, tracked, and mitigated
throughout the design process.”
With the trend towards larger and more
diverse infrastructure projects, Kiewit
has been able to take advantage of its
company structure to bring in the most
qualified management and equipment
from across the company to pursue and
build the work. Notes Salamie, “when it
comes to infrastructure work, there is no
skill set that we can’t provide within our
diverse organization.”
The new methods impact the company’s
personnel and risk-mitigation decisions,
notes Salamie. “Given the increase in
alternative-delivery methods, we have
made changes in the skill sets of our
management. We have added designers
and design coordinators to our staff to
optimize and manage the design process
and improve constructability.”
Environmental concer ns also are
g ro w i n g i n i m p o r t a n c e , m a k i n g
projects more complex and impacting
bid decisions. “Environmental
compliance, safety, and the legal
side of overall compliance consume
an ever-increasing percentage of
o u r p ro j e c t s t a ff ’s d u t i e s , ” s a y s
Salamie. “In today’s world of project
management, our staff has to be part
designer, part environmental engineer,
part safety specialist, and part lawyer.
That became necessary on design-build
projects, as the company was given
responsibility for the design process.
“No longer is the bridge design a black
box for our construction team, where all
Environmental
Concerns Grow
Maryland’s Intercounty Connector
(ICC) project shows the requirements
Kiewit’s 130 Years of Service
Kiewit traces its history to 1884, when two brothers formed a masonry contracting partnership
in Omaha, Neb. Now, 130 years later, it’s grown into one of the largest construction and mining
companies in North America.
The firm entered the heavy and highway construction markets during the Great Depression as
building construction disappeared. It also grew during World War II, as it took on a variety of
projects for the military, including barracks, airfields, and other facilities throughout the west.
Its government work continued through the Cold War years. Kiewit played a key role in building
the interstate highway system, especially some of its most difficult sections.
In the 1980s, Kiewit made significant investments in ventures outside its core businesses, with
an emphasis on energy and telecommunications. During the 1990s, it became a leader in designbuild and engineer-procure-construct delivery methods.
Today, through its operating companies, Kiewit generates revenues of more than $11 billion and
is consistently ranked among the top five contractors by Engineering News-Record. It is one of the
largest employee-owned businesses in the country.
The $550-million, 7-mile-long Intercounty
Connector Contract B project in Maryland
features 10 precast concrete bridges that had to
pass over sensitive stream valleys and two local
watersheds.
needed today. The Kiewit-led MD200
Constructors’ $550-million bid for
Contract B consisting of 7 miles of
the 18.8-mile-long project—said to
be the highest monetary contract the
state has ever awarded—was won
due to its proposed environmentalmanagement program. The bid was
slightly higher than others, but “the
owners were searching for the team
that offered the best value for this
high-profile and highly debated,
design-build contract,” said Gwyon
Nelson, the Kiewit sponsor who
served as the ICC-B project manager.
The environmentally sensitive project
crosses stream valleys and two local
watersheds with specific streamclosure periods. “W ith no tested
designs to fall back on, we had to
determine what a project with such
ambitious environmental goals would
look like,” says Nelson. The project
included 10 bridges, built using
precast concrete components.
Cost control becomes a key aspect
of complex projects, notes Salamie.
“Material escalation is a consideration
for all our project pursuits, especially
for steel components on longduration projects.”
Kiewit’s Bridge to Prosperity
Nine Kiewit employees traveled to Nicaragua in February to put their bridge-building skills to work
for the citizens of Cinta Verde near the rural El Limon River. The project, sponsored by Bridges to
Prosperity, used concrete footings and anchor blocks along with steel towers and a timber deck,
to link the village to schools, medical care, and markets on the other side of the river. It also served
as a training exercise to teach the village’s 300 people to build more bridges.
Kiewit’s construction team faced the challenges of building with primitive materials and tools,
overcoming language barriers, and living with no electricity, says Kiewit’s Ralph Salamie, project
manager. “Kiewit’s culture thrives on strong values, and we share our bridge-building talents with
people in need.”
Bridges to Prosperity has built more than 70 footbridges in 18 countries. Ten bridges are planned
for Nicaragua in 2014. The Cinta Verde Bridge took about 10 days to construct.
Kiewit and its partner, International Bridge Technologies (IBT), each contributed $25,000 to
design and construct the 115-ft-long suspension footbridge. The volunteers paid their own travel
expenses and contributed a week of time, with Kiewit donating a second week for each volunteer.
Kiewit employees raised another $2000 to deliver maps, textbooks, sports equipment, and supply
kits to the local school.
Mitigating risk also requires picking
subcontractors and design partners
carefully. “For design-build projects,
we look for design teams with proven
track records of minimal ‘design
growth,’ maintaining a schedule, and
understanding the constructability
side of the design,” says Salamie.
“We involve our experienced builders
at bid time to review each element,
ensuring we won’t have to modify
the final design for constructability
reasons.” Kiewit also includes a
second-check design team to mitigate
the risk of errors.
Concrete Use Increases
These evolutions have led to specifying
concrete materials more often. “My
experience on every design-build project
has been that our first choice is to go
with concrete, due to its speed, cost,
and shorter lead times than structural
steel,” says Thomsen.
The emphasis on service life also has
driven this preference, says Oscar
Antommattei, senior concrete engineer.
“We see a trend among clients wanting
a longer service life, so we are pushing
concrete to provide more performance,”
he says. “We look at cementitious
materials, durable aggregates, and
obtaining a lower water-cementitious
materials ratio to achieve this. We
evaluate various concrete mix designs,
because each region of the country
has different materials that create
unique challenges to achieve workable
mixes that can also meet service life
requirements. It can be challenging to
get the right mix design.”
That’s another benefit of the designbuild method, he notes. “In designbuild, we can look at the entire
structure to find ways to combine
techniques to protect against corrosion
and improve service life.” These can
include adding post-tensioning and
providing alternatives to traditional
reinforcement, such as epoxy-coated
reinforcement and, more recently,
galvanized or stainless steel options.
Kiewit used self-propelled modular transporters to move a cast-in-place, post-tensioned box-beam structure with a curved shape into place in one day on
Pecos Street over I-70 in Denver, Colo. During one weekend closure, the existing bridge was demolished, the bridge travel path was constructed with metal
plates and fill material, the bridge was moved into place, and the travel path was removed.
Kiewit combined concrete segmental and cable-stayed technology to design and build the Portland-Milwaukie Light-Rail Transit Bridge for TriMet in the
Portland, Ore., metro area.
Concrete components also are helping
to meet owners’ tighter scheduling
demands. “Accelerated bridge
construction techniques have become
a trend throughout the industry,” says
Thomsen. “Project owners are seeing
the value in bridge construction while
minimizing the impact to the traveling
public. Prefabricating components and
delivering standardized pieces have
helped achieve those goals.”
Adds Antommattei, “Precast concrete
can provide significant benefits relating
to the schedule. Multiple elements
can be fabricated rapidly and in
advance of their need: then stored
and held until the job requires them.
Additionally, precast concrete elements
are fabricated under more controlled
placement conditions and under strict
quality-control measures, which helps
ensure that strength and durability
requirements are met.”
Concrete
Capabilities Expand
“Concrete bridge elements are heavier
than comparable steel components,
but as high-performance concrete
pushes the limits to higher and higher
s t re n g t h s , m e m b e r s a re g e t t i n g
progressively more slender and lighter,
improving the competitive advantage of
concrete structures,” said Salamie.
stayed bridge was chosen for its
minimal environmental impact and
aesthetics.
Span lengths also are increasing, he
adds, which is expanding the market
for concrete girders. “Bulb-tee girders
made of high-performance concrete let
us extend lengths to 200 ft and beyond.
That opens up more opportunities for
concrete bridges, which we used to cap
at about 120 ft.”
“C ombi ni ng c onc rete s egment al
technology with relatively new cablestayed technology presented many
unique challenges to our design and
construction team,” says Salamie.
Segmental bridge designs are growing
in popularity, Salamie says. “Concrete
segmental and cable-stay construction
can add benefits if there is restrictive
access for falsework or erection
equipment, such as over water or wide
roadways.”
Those spans are carrying more than
v e h i c l e s t o d a y, w i t h p e d e s t r i a n
bridges growing in use and light-rail
applications becoming popular. “We’re
seeing more transit projects with
elevated guideways when there’s no
space for them at ground level,” says
Salamie.
One of the most innovative of those
projects is being built for TriMet
in the Portland, Ore., metro area,
which awarded Kiewit a $119-million
design-build contract for the PortlandMilwaukie Light Rail Transit Bridge.
When completed in 2015, it will
be used by light-rail trains, buses,
streetcars, bicyclists, and pedestrians.
The cast-in-place segmental, cable-
Such innovations will keep Kiewit
competitive even as new demands and
new delivery systems arise. “We’re
doing more segmental and cable-stayed
bridges and other types of unusual
designs, but our bread and butter
remains the simple span girder bridge,”
Salamie says. That may be the only
thing that’s simple about the projects
Kiewit builds today.
For additional photographs or
information on this or other projects,
visit www.aspirebridge.org and open
Current Issue.
PERSPECTIVE
Bridge
Information Modeling
Are We There Yet?
by Barbara Day and Shri Bhide, Bentley Systems Inc.
Bridge information modeling (BrIM) has
become an important industry tool since it
was first introduced to the transportation
sector. BrIM is an innovative approach to
bridge design, construction, operations,
and project delivery. It allows for the
creation of an information-rich data model
that can be used during the life of the
bridge, connecting design, construction,
operations, and maintenance.
More than ever, bridge professionals are
seeking methods to:
• reduce construction costs with more
economical designs,
• improve quantity take-offs,
• model the step-by-step construction
process in 4D, and
• realistically visualize projects with
imagery and virtual drive-throughs.
The Federal Highway Administration
MAP-21 compliance requirements,
and the growing popularity of designbuild and Public-Private Partnership
projects, have set the stage for greater
owner expectations for faster and moreefficient methods of constructing our
transportation assets. Bridge designers
need to be prepared for this shift in
workflows.
Information modeling allows more time
for evaluating different alternatives,
simulating different scenarios, and
optimizing your eventual design. All
images: Bentley Systems Inc.
The BrIM design environment has
been a headlining discussion at
conferences and committee meetings,
in articles, and on social media. These
discussions are an opportunity for
research results and best practices to
meet new contractual requirements
to select the best solution to design,
build, maintain, and operate these
assets. While the infrastructure needs
increase, new methods to expedite
projects, manage funds more wisely,
and meet the demands of the
public—who want minimal disruption
to their traffic patterns—are needed.
Current trends indicate that the
transportation industry is slow to
adopt BrIM workflows and methods.
It is unclear whether the industry is
waiting for industry standards, if it is
uncomfortable with change, or both.
The perceived challenges associated
with implementing a BrIM approach
are:
• a change in workflow would
detract from billable design time,
and
• whether it is worth it.
Considering the benefits versus the
risks, a traditional workflow can
be best described as a fragmented
flow of information and it is likely
approached from a ‘data ownership’
perspective. Those responsible for
their component of the project own
their information and minimal data
are sometimes shared.
For example, the highway engineer
designs the alignment, profile, and
superelevation of the structure based
on a typical bridge section. The bridge
engineer takes that information
and re-enters these data into the
structural design software to design
Interactive inspections allow for
collection and reporting of condition
data at the component level.
Fully augmented models transfer
structural component data directly to
field inspection technology.
the bridge. Following completion of
the design, the work is turned over to
the detailers who draw the structural
sections and reinforcement details
based on the engineer’s preliminary
drawings or even paper sketches.
In this non-automated workflow, any
changes or updates to the design are
left to the engineers to inform their
peers of modifications made. The
documented effects of this current
workflow translate into project risks,
including errors introduced with data
re-entry and scattered data across
an organization or organizations.
Each person only knows where their
piece of the workflow is—and the
same data may be held in different
locations.
BrIM Environment
Wo r k i n g i n a B r I M e n v i ro n m e n t
eliminates these gaps in shared data.
A lot of the information generated
during a typical design workflow
can easily be adapted into a BrIM
workflow with increased productivity
and efficiencies. The key components
One of the advantages of publishing
a BrIM model is the effective and
efficient sharing and distribution of
information, which can reduce errors,
compress the project schedule, and
reduce project costs. BrIM models are
widely reusable, enabling teams to
reference, repurpose, and republish
content, including business properties,
geometry, graphics, and the respective
component relationships. The asset
information can be queried or the
components linked to construction
documents and 2D plan sets. These
design data also can be fully utilized
by inspection software and seamlessly
accessed in the field for collection
and reporting of the asset via mobile
technology.
buildingSMART to extend the
IFC standard to bridges. A recent
research study at the State University
of New York at Buffalo found that
Bentley’s ISM can be used to create
data models for the most common
concrete and steel bridges. Additional
work is necessary in ISM to extend its
applicability to complex bridge types
and roadway information.
Data re-use and
mobility are a necessity.
are already in place; transferring to
a BrIM workflow is likely a matter of
assessing data mobility and adjusting
the gaps. BrIM is a collaborative way
of doing business and can be a key
component for success in firms of all
sizes.
A typical BrIM workflow would
involve all stakeholders, from all
relevant disciplines, to be involved in
developing a fully intelligent, living,
cradle-to-grave model. Data sources
can include information from the
geotechnical, survey, civil, and bridge
disciplines. In the design of the bridge,
these same data are used to create a
global-intelligent, three-dimensional,
as-designed physical model. This
global model can then be augmented
with miscellaneous components
such as lighting or signage, thereby
becoming the single source of data for
the asset.
D a t a re - u s e a n d m o b i l i t y a re a
necessity for any type of welldesigned, constructed, and maintained
asset. Having the right version of data,
the right format, and the required
level of precision available to the right
people at the right time is a clear
differentiator in this workflow.
Data model standards commonly used
for building structures include CIS/2
(CIMSteel Integration Standards), IFC
(Industry Foundation Classes), and
Bentley’s ISM (Integrated Structural
M o d e l i n g ) . H o w e v e r, t h e re i s n ’t
one currently available for bridges.
There are efforts underway at
In many ways, the bridge industry
i s re a d y t o e m b r a c e B r I M . T h e
potential is there for state-of-theart deliverables with assurance
of accurate results. This year could
be the one that BrIM gains traction
and places the bridge industry in a
position to meet our infrastructure
needs, quicker, less expensively, and
confidently.
Publishing this vital as-designed
information is more than a plan set.
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PROJECT
ZILWAUKEE BRIDGE
Bearing replacement need determined after 18 years of service
by Corey E. Rogers, Michigan Department of Transportation
Opened to traffic in 1989, the
325-ft-long approach spans and
393-ft-long river span of the Zilwaukee
Bridge rise to 125 ft above the Saginaw
River to accommodate marine shipping
traffic. The bridge is a 1.5-mile-long twin
concrete segmental structure comprised
of 1592 precast concrete segments, each
weighing an average of 160 tons. It was
the largest precast concrete segmental
project in the United States at the time.
The 25-span northbound structure and
26-span southbound structure carry I-75
traffic over the Saginaw River through
the city of Zilwaukee, Mich.
The Zilwaukee Bridge was designed
to the 1973-77 AASHTO Standard
Specifications, with HS-25 live loading
and AASHTO Zone 1 seismic loads. The
single-cell segments of the superstructure
box girder are approximately 73 ft wide
at the top flange, 36 ft wide at the
bottom flange, and vary in depth from 8
ft at midspan to 20 ft at the piers. Each
structure contains eight, in-span, quarterpoint hinges to accommodate expansion
and rotation from thermal gradients.
Bearing Problems
Originally, the superstructure rested
on high-capacity pot bearings at the
piers and expansion joint locations.
The pier bearings were mostly fixed
with one of the two pier bearings
allowing transverse movement. The
elastomer pot bearings allowed
for 0.04 radians of rotation and
accommodated 12 in. of longitudinal
and/or transverse movement via the
polytetrafluoroethylene (PTFE) sliding
surface.
Bearing problems were identified during
the first detailed inspection in 1993.
Neoprene elastomer was leaking from
the sealing ring around the pot piston
at the expansion hinge and pier bearing
locations. This reduced the rotational
capacity of the bearing. There were
also indications of wearing in the PTFE
sliding surfaces, which was jeopardizing
thermal movements of the bridge.
At some pier locations, the loss of
elastomer resulted in contact between
the top sole plate and the bottom
masonry plate edge. In 2007, the
Michigan Department of Transportation
(MDOT) began discussions to replace
the 104 pier bearings and 34 expansion
joint bearings and upgrade the bearings
to current AASHTO service criteria.
Bearing Replacement
The challenges associated with the
bearing replacement were clear. Loads
approaching 17 million pounds would
The Zilwaukee Bridge, a 1.5-mile-long
twin concrete segmental structure,
carries I-75 traffic over the Saginaw River.
All Photos: Michigan Department of
Transportation.
profile
ZILWAUKEE BRIDGE / ZILWAUKEE, MICHIGAN
BRIDGE REPLACEMENT CONSULTANT: T.Y. Lin International, San Francisco, Calif.
QUALITY ASSURANCE ENGINEER: Janssen and Spaans Engineer Inc., Chicago, Ill.
CONSTRUCTION ENGINEER: Corven Engineering Inc., Tallahassee, Fla.
PRIME CONTRACTOR: PCL Construction, Tampa, Fla.
POST-TENSIONING CONTRACTORS: PCL Construction, Tampa, Fla., and Walter Toebe Construction, Wixom, Mich.
have to be jacked from piers with
heights up to 130 ft. Then, new, higher
capacity bearings would have to be
installed into the existing openings with
little to no allowable modifications to
the structure.
Loads approaching
17 million pounds would
have to be jacked from
piers with heights up to
130 ft.
The old expansion joint bearings rested
on reinforced, cantilevered concrete
corbels containing the anchorages for
the post-tensioning. Therefore, any
modifications to the concrete corbel
to gain additional space was limited to
the 2 in. of concrete cover above the
reinforcing steel. The existing opening
housing the expansion joint bearings
provided approximately 4 in. of space
from corbel to top plate. The top plates
were salvaged because they were cast
into the upper segment and were in
sound condition. This lack of space also
meant a higher-capacity and taller potstyle bearing would not be able to be
used.
Post-tensioned waler configuration, compression collars, and jack layout at pier bearing.
New Contracting Methods
Due to the uniqueness of the bearing
replacement project and the associated
challenges, MDOT opted to use a
construction management/general
contractor (CM/GC) contracting method.
This method
allowed for greater
flexibility during
construction.
The pier bearings rested directly
on top of each pier with a cast-inplace concrete plinth between the
top of bearing and bottom of the
superstructure. Plinth modifications
were made to accommodate various
bearing depths. Jacking stresses
and load path redistribution were
addressed by application of additional
external post-tensioning forces via
post-tensioning bars and walers to
the elements affected. Some of the
affected elements required an additional
2.5 million pounds of compression to
prevent excess principal tensile stresses
during jacking.
Erection of pier column work platform.
MICHIGAN DEPARTMENT OF TRANSPORTATION, OWNER
BEARING SUPPLIER: RJ Watson Bridge and Structural Engineered Systems, Alden, N.Y.
PROJECT DESCRIPTION: Pier/abutment bearing replacement, expansion joint bearing replacement, deck patching, barrier wall repairs, epoxy healer/
sealer, and lighting upgrades
STRUCTURAL COMPONENTS: 104 pier bearings, 34 expansion bearings, 10 abutment bearings
BRIDGE REPAIR COST: $36 million
$36 million, and the contract moved
into the second, or general contractor,
phase.
Checks
Pier column compression collars.
Newly installed pier disk bearing with
pressure grouting formwork.
This method allowed for greater
flexibility during construction of such a
complicated project. An example of this
flexibility occurred during the construction
management phase and involved the
jacking scheme for the pier bearings.
Early designs called for shoring
towers that would support the jacked
superstructure from the footings.
The contractor proposed placing the
jacks on top of the pier columns and
horizontally compressing the tops of
the columns with pier collars to confine
them and prevent column edge spalling
at jack bearing locations. This method
was determined to be feasible and
eliminated the need for costly shoring
towers.
It was also during the construction
management phase that MDOT decided
to use disk bearings instead of pot
bearings. The disk bearing is simpler in
design and thinner than a pot bearing,
but requires a larger footprint. A
polyurethane disk provides the required
rotational capacity and a stainless steel
top plate coated in PTFE provides the
lateral movements. The disk bearings
were able to fit into the 4-in.-deep
opening at the expansion joints and
provide the needed bearing capacity at
pier bearing locations. Upon completion
of the design phase, a guaranteed
maximum price was negotiated, with
the final cost of the project totaling
Construction began in April 2013
with the closure of the southbound
structure. MDOT required the contractor
to demonstrate a complete pier and
expansion bearing replacement prior
to commencing production mode.
This allowed MDOT inspectors and
construction engineers to become
comfortable with the entire replacement
operation and work through any design/
constructability issues before work
began at multiple bearing locations.
The contractor submitted a detailed
jacking procedure for MDOT approval.
MDOT also created specialized jacking
forms for inspection staff to use during
all jacking operations. Any deviations
from the procedures or forms resulted
in an immediate stoppage of work and
reevaluation of the procedure.
Ground penetrating radar was used at
all proposed coring locations. Chipping
was allowed to visually verify the tendon
locations. Coring was conducted in the
web walls for diaphragm strengthening
and in the deck for strongback
installation and platform erection.
Platforms weighing approximately 90
tons were designed and constructed by
the contractor and hoisted into place at
the top of the piers with hydraulic jacks
and high tensile rods. Twelve 1¾-in.diameter post-tensioning rods were
installed transversely through the box
at most of the pier diaphragm locations
and stressed to 210 kips each to support
the 12 ft by 25 in. load redistribution
walers. The smaller diaphragm locations
received modifications by placing
reinforced, post-tensioned concrete
blocks adjacent to the diaphragm and
over the jacking points. The larger
diaphragms received no strengthening
modifications.
Two 2½-in.-diameter post-tensioning
rods held the compression collars
and were stressed to 540 kips each.
Up to eight 600-ton hydraulic jacks
per bearing were used to lift the
superstructure from the bearings.
Steel rods were anchored into the pier
and bottom of the superstructure,
and surveys were used to monitor
displacement. The existing bearings
and concrete plinth were then removed
with the use of a wire saw, the new
steel reinforcement was anchored with
epoxy into the top of the pier and
bottom of the superstructure, and the
new disk bearings were set into place.
Pressure grouting of bearing pedestals
with a non-shrink cementitious grout
was conducted and allowed to reach a
compressive strength of 5 ksi prior to
lowering the structure.
The expansion joint bearings were
replaced with the use of a strongback
system. Overhead and underslung
beams spanning the width of the
b o x w e re s u p p o r t e d b y t w e l v e
2½-in.-diameter post-tensioning rods
stressed to 460 kips each. Four 400ton hydraulic jacks were used to lift
the supported span. The old bearings
were then removed and the new disk
bearings installed and grouted into
place.
Due to the excessive movements
associated with the thermal gradient,
MDOT decided all jacking and lowering
operations be conducted between 7
and 9 a.m., when the structure has the
least thermal movement. This provided
consistency in the jacking displacements
and ensured no new stresses were being
introduced into the bridge upon release
of the jacks.
Concluding Remarks
The bearing replacement on the
southbound structure was successfully
completed ahead of schedule in
November 2013. Much of the
success can be attributed to the
group of contractors, subcontractors,
consultants, designers, and MDOT staff
that continually found solutions when
confronted with challenges, and who
had a great sense of ownership and
pride regarding the project. There was
no template for a project like this and
many of the procedures were drafted
as needed. MDOT was able to gain
valuable experience on a complex
bridge, built by a previous generation.
____________
Corey E. Rogers is the bridge construction
engineer with the Michigan Department
of Transportation in Lansing, Mich.
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FULL-SPAN
PRECASTING OF
RAILWAY BRIDGES
by Marco Rosignoli, HDR Inc.
Span stacking on support frames. Photo: Systra.
In recent years, more than 35,000
spans of high-speed railway (HSR)
bridges have been built in China and
large investments in HSR infrastructure
have been made in Europe, Japan,
Korea, and Taiwan. Long prestressed
concrete (PC) bridges are the typical
solution for HSR infrastructure on poor
soil. The combination of long bridges
and short spans results in a large
number of modular spans. This allows
for investments in large precasting
facilities and special means for beam
transportation and erection.
L i g h t - r a i l t r a n s i t ( L R T ) p ro j e c t s
also include miles of PC elevated
guideways. Many HSR bridges and
the first new-generation LRT bridges
have been built with precast concrete
beams. Precasting offers rapid
construction and repetitive casting
processes in factory-like conditions. The
beams can be erected all year round
in almost any weather conditions.
This article illustrates the application,
transportation, and erection of fullspan precast concrete beams for LRT
and HSR bridges.
Precasting offers
rapid construction
and repetitive casting
processes in factory-like
conditions.
functions, and the possibility of lowering
the vertical profile by 5 to 6½ ft.1
U-beams for LRT Bridges
Dual-track precast concrete segmental
box girders have been used intensively
for LRT bridges. Single-track, precast
concrete U-beams, however, are being
used more frequently because of their
higher quality and faster erection rate.
A single-track U-beam is 15 to 18 ft
wide, weighs from 340 kips for
82-ft-long spans to 500 kips for
115-ft-long spans, and is typically
transported on the ground with trucks
and rear steering trolleys. Different
proportions of pre- and post-tensioning
are possible. Pretensioning simplifies
forming and diminishes the cost of
prestressing, but requires anchor
bulkheads and reaction beams designed
for the prestressing force of many
strands.
Single-track U-beams include two edge
girders and a bottom slab that supports
the track via ballast or direct fixation.
The edge girders keep the train on the
bridge in case of derailment, and the
top flanges are used as walkways for
passenger evacuation. Precast concrete
beams offer simple casting operations,
r a p i d a n d i n e x p e n s i v e e re c t i o n
with ground-based cranes, optimal
integration with the urban environment,
built-in sound barrier and system
The fabrication process is consistent
with the speed of erection. Storage for
completion of curing is necessary only
when the beams are delivered on the
completed deck. Ground transportation
and crane erection require two to three
days of curing, and the beams can
complete curing on the piers. A small
storage area may be needed to provide
some flexibility in case of delivery delays
or defective beams. In typical conditions,
the beams are picked up from the
pivot for 360-degree rotation of two
paired wheels controlled by a steering
computer. Long transverse beams ensure
lateral stability and align the wheels of
the trolley with the superstructure webs
for direct loading. The load in the wheels
is equalized electronically.
An articulated saddle supports the rear
end of the beam and rolls along the
main beam during beam extraction. Two
fixed blocks support the front end of the
beam and provide the torsional restraint
during transportation.
Span Launchers
Span transfer to the storage platform with a portal carrier with pivoted tractors. Photo:
Marco Rosignoli.
casting bed and loaded onto the truck
for just-in-time delivery.
HSR Bridges
The precast concrete beams for HSR
bridges are too heavy for ground
transportation and need to be
delivered on the completed deck and
positioned with dedicated machines.1
The productivity of the precasting facility
matches the productivity of the erection
lines. The size of the storage area and
the number of storage platforms are
based on the curing time required prior
to delivery, which depends on the type
of beam transporter.
The beams are often designed for
post-tensioning to facilitate handling
of prefabricated cages and to shorten
the curing time in the casting bed.
Combinations of pre- and posttensioning are also possible. Partial
post-tensioning is applied after 12 to
18 hours of curing to make the beam
self-supporting for transfer to the
storage area. Parallel casting lines are
separated by transportation routes for
cage delivery and removal of the beams.
Three casting beds may be used in the
casting lines for single-track U-beams
in combination with an inner form that
shuttles back and forth along the casting
line. 1 Alternatively, the inner tunnel
forms for box girders are more complex
to operate and may be stored between
two casting beds to serve them. Casting
beds and handling equipment for dual-
track box girders are more expensive
than for single-track U-beams, but the
number of units is halved.
Portal cranes on rails or steering wheels
are used to move the beams around
the precasting facility. Portal cranes with
transverse tractors and steering wheels
facilitate access to casting beds and
storage platforms. Portal cranes with
pivoted tractors are also used for beam
delivery and placement.
The typical configuration of a span
launcher includes a rear main frame and
a front underbridge. The underbridge is
supported at the leading pier of the span
to be erected and at the next pier. The
front end of the main frame is supported
on the underbridge during launching
and on the leading pier cap during beam
placement. A C-frame supports the rear
end of the main frame and allows the
precast concrete beam to pass through.
The main frame cantilevers out behind the
rear C-frame to store two winch trolleys
for beam removal from the tire trolley.
Tire Trolleys
Tire trolleys are used to transport the
beams along the access embankment
and completed superstructure to the
rear end of the launcher. The tire trolleys
have 135- to 200-kip capacity and the
speed varies significantly from machine
to machine. The main beam of the
trolley is supported by multiple transverse
beams. Each transverse beam has a
Tire trolley for 900-kip, single-track box
girders. Photo: BWM.
Telescopic span launcher for 107-ft-long,
2023-kip, dual-track beams. Photo: BWM.
forward until the front tractor is over the
saddle, and the vertical cylinders of the
saddle are activated to lift the tractor
from the deck. The hydraulic motors of
saddle and rear tractor are synchronized,
and the carrier is moved along the
underbridge until the front tractor is
beyond the leading pier.
After reaching the span lowering
position, the saddle pushes the
underbridge forward to clear the area
under the carrier for span lowering. After
positioning the beam, the underbridge is
moved back to release the front tractor
onto the new span for a new placement
cycle.1
Portal carrier positioned for span lowering. Photo: Marco Rosignoli.
and fast. Multiple shorter bridges are
better handled with portal carriers.
Portal Carriers
with Underbridge
Repositioning of the underbridge. Photo:
Marco Rosignoli.
Loading the launcher is relatively simple.
The tire trolley is driven under the rear
overhang of the main frame, the front
winch-trolley picks up the front end of
the beam and moves forward, and when
the rear support saddle reaches the front
end of the tire trolley, the rear winchtrolley picks up the beam to release the
tire trolley.
The beam is moved out and lowered to
the deck level. Load cells and stainless
steel shims are used to adjust the support
reactions. Placing the beam takes two
to three hours and repositioning the
launcher takes another two to three
hours, so two to three beams can be
placed every day when crossover
embankments exist along the delivery
route and the precasting facility is
designed for such production.
Beam launchers fed by tire trolleys
are preferred for very long bridges, as
the launcher is not used for beam
transportation and the trolleys are stable
A portal carrier comprises two wheeled
tractors connected by a box girder that
supports two hoists. The tractors have
motorized steering wheels controlled by
steering computers.1 In some machines,
the tractors rotate by 90 degrees for the
lateral movements of the carrier; in other
machines the wheels turn by ±90 degrees
individually.
To pick up the beam from the casting
bed, the carrier is moved alongside the
beam and the tractors are rotated by 90
degrees; rotation is not necessary when
the carrier has ± 90 degree steering
wheels. The carrier is driven laterally
over the beam, lifts the beam, is driven
back to the transportation route, and
is realigned with a reverse sequence of
operations. The same operations are
repeated to release the beam into the
storage area and to pick it up for final
delivery.
At the leading end of the erection
line, the carrier reaches a two-span
underbridge. The underbridge is a stiff
box girder supported on self-launching
pier frames at the two piers of the
span to be erected and at the next pier.
A motorized saddle rolls along the
underbridge and carries vertical support
cylinders for the front tractor of the
carrier.
The saddle is moved to the rear end of
the underbridge, the carrier is driven
Beam lifting takes one to two hours,
placement takes three to four hours, and
transportation may take an entire day
when the delivery route is long. When
the precasting facility has two casting
lines, each carrier serves a casting line.
Two carriers and two underbridges
may be used to erect two bridges
simultaneously. Two carriers may also
work with a common underbridge to
double the erection rate of one bridge
when crossover embankments exist along
the delivery route.
Portal carriers are the first-choice solution
for construction of multiple HSR bridges
separated by embankments or tunnels.
The carrier picks up the underbridge from
the landing embankment and moves it to
the next abutment without dismantling.
Immediate restart of beam placement
minimizes disruption of precasting
facilities designed for just-in-time delivery.
Reference
1. R o s i g n o l i , M . 2 0 1 3 . B r i d g e
Construction Equipment, 496 pp.,
ICE Publishing, ISBN: 978-072775808-8.
____________
Marco Rosignoli is the bridge technical
leader in the Tappan Zee Project Office of
HDR Inc. in Tarrytown, N.Y.
EDITOR’S NOTE
This article is an abbreviated version of a
paper published in the Spring issue of the
PCI Journal. The full version is available
at www.aspirebridge.org and click on
Resources.
the search for excellence
the 2014
design awards
The 52nd annual PCi design awards program is now
accepting entries. Join us in the search for excellence and submit your
projects electronically by May 19, 2014.
Visit www.pci.org and click on the “2014 PC Design Awards” link for more
information and submission details.
Contact: Jennifer Peters, [email protected] or
Brian Miller, P.E., LEED AP, [email protected]
PROJECT
Rehabilitating Boston’s commuter rail line
by Aboud Alzaim, Malek Al-Khatib, and Daniel Deng, The Louis Berger Group Inc.
Commuter rail train (inset) passing over one of the new bridges. All photos: The Louis Berger Group Inc.
In 2010, the Massachusetts Bay
Transportation Authority (MBTA)
determined that two, century-old rail
bridges over the Neponset River had
reached the end of their fatigue service life.
The bridges, which are on the Fairmount
commuter line, connect the Fairmount
and Readville stations in the Hyde Park
neighborhood of Boston.
limits, but replacing them posed several
challenges. There had to be a minimum
disruption of traffic, which required a
phased construction plan. Work needed
to be done quickly under tight constraints
at the site, without fouling the adjacent
track. The new structures were to require
minimal future maintenance, with no
fatigue concerns.
Both bridges were structurally deficient,
with fatigue ratings below statutory
Given these constraints and economic
considerations, the design engineer
profile
proposed a long-span, precast, prestressed
concrete New England bulb-tee beam
bridge. This type of bridge reduces
material costs, future maintenance, and
environmental impact, while also improving
aesthetics in the surrounding area.
The bulb-tee beam optimizes the strengthto-weight ratio, maximizing the carrying
capacity for live loads. At the same time,
the wide top flange of the bulb-tee beam
eliminated the need for formwork when
FAIRMOUNT LINE BRIDGES / BOSTON, MASSACHUSETTS
BRIDGE DESIGN ENGINEER: The Louis Berger Group Inc., Morristown, N.J.
PRIME CONTRACTOR: S & R Construction Enterprises Inc., Newton, N.H.
GEOTECHNICAL ENGINEER: GEI Consultants Inc., Woburn, Mass.
PRECASTER: Northeast Prestressed Products LLC, Cressona, Penn.—a PCI-certified producer
OTHER MATERIAL SUPPLIERS: High load multi-rotational bridge disc bearings, The D. S. Brown Company, North
Baltimore, Ohio
Bridge Resiliency
North approach view of the two main tracks looking north on bridge 2 over the
Neponset River bridge.
constructing the bridge deck. Additionally,
the concrete deck was built immediately
after erection of the beams, which
shortened the construction duration of
the project. Using precast concrete beams
with a ballasted deck also prevented
construction debris from falling into the
river, improving environmental sustainability
and protecting recreational users of the
river below.
History and Condition
of Bridges
The two former bridges dated
back to 1906. Bridge 1 was partially
reconstructed in 1952 and again in
1974. The bridge was a 56-ft 8-in.-long,
single-span steel structure carrying four
tracks: two main line tracks and two
spur tracks with one owned by the CSX
Freight Line. This open deck-type bridge
had open steel grates as walkways
between the tracks and on cantilevers
on both sides of its outer girders. The
superstructure consisted of four pairs of
steel girders, with each pair of girders
supporting one track. The total width
was 61 ft 9 in.
Bridge 2 carried two main line tracks.
The bridge was an 89-ft 3-in.-long
single span steel structure with a
30-degree skew. The out-to-out open
deck width was 22 ft 10 in. and used
timber planks as a walkway between
the tracks. Its superstructure consisted
of two pairs of steel riveted builtup girders supporting the main line
tracks.
As an alternative to demolishing all
the components of the old structures,
the design engineer developed a
To ensure the bridges’ durability and ability
to accommodate Cooper E-80 loads, highperformance concrete (HPC) was used to
construct the bulb-tee beams, allowing
the structure to resist higher loads with a
more efficient cross section. The minimum
specified 28-day concrete compressive
strength was 10 ksi for the prestressed
concrete bulb-tee beams, 6 ksi for the
rock-socketed drilled shaft foundation, 5
ksi for the bridge deck, and 4.5 ksi for the
walkway slab. Due to the weight of the
concrete beams, the bridge is less prone
to vibration-induced damage than a steel
structure. These HPC beams in particular
are anticipated to have an operational life
span of 75 years.
The project was finished six months ahead
of schedule, without any change orders,
and is testament to the versatility of
precast concrete.
hybrid design. For the main line
tracks, two new bridge structures
were selected to replace the existing
bridges, while only the superstructure
was replaced for the spur tracks of
bridge 1.
Construction
Staged construction was planned around
train operations and other concurrent
Elevation of one of the longest
prestressed bulb-tee beams on bridge 2.
MASSACHUSETTS BAY TRANSPORTATION AUTHORITY, OWNER
PROJECT DESCRIPTION: Replacement of two existing steel railway bridges carrying two main line tracks with two new bridges using New England
bulb-tee (NEBT) concrete beams
STRUCTURAL COMPONENTS: Bridge 1: a 71-ft-long, 37-ft-wide, single-span bridge with seven prestressed NEBT 1400 beams. Bridge 2: a
104-ft-long, 36-ft-wide, single-span bridge with seven prestressed NEBT 1800 beams. Both bridges have cast-in-place intermediate and end diaphragms,
cast-in-place 10- to 12-in.-thick concrete deck, and 4-ft-wide cantilevered walkways on both sides with six 4-in.-diameter PVC conduits for signal and
communication cables suspended from underneath. The substructure for each bridge consists of four, 3-ft-diameter drilled shafts with lengths, including
6-ft-deep rock sockets, ranging from 98 to 117 ft for bridge 1 and 50 to 78 ft for bridge 2.
BRIDGE CONSTRUCTION COST: $8.6 million
AWARDS: PCI 2013 Design Award for Best Non-Highway Bridge
36’–0”
CL G1
CL G2
CL G3
CL G4
CL G5
CL G6
CL G7
6 SPACES @ 4’–0” = 24’–0”
Typical cross section of bridge 2. Drawing: MBTA.
Crane load transfer during beam
erection.
c o n s t r u c t i o n p ro j e c t s a l o n g t h e
Fairmount line. As a result, the bridges
were built in two phases: the main line
tracks were taken out of service one at
a time, allowing the contractor to use
the second track on weekends when
passenger trains do not run. However,
because both spur tracks were needed
throughout the week, the spur track
superstructure was replaced under
accelerated construction techniques
during one weekend shutdown.
Precast, prestressed concrete bulbtee beam structures were determined
to be the most economical for the
main line bridges. A preliminary
design was prepared to estimate the
comparative costs of materials; based
on this prototype, the cost of steel was
estimated at $3,346,000 compared
with $1,363,000 for concrete.
Additionally, the maintenance cost for
a steel bridge would be much higher
than that for a concrete one, especially
because the bridge is over the river
with limited accessibility.
The new bridge abutments were
designed as stub abutments supported
on four, 3-ft 6-in.-diameter drilled
s h a f t f o u n d a t i o n s . To m i n i m i z e
outage time, the new substructures
were constructed behind the existing
abutments. As a result, the span
lengths of the new bridges increased
to 71 and 104 ft for bridges 1 and 2,
respectively.
The bulb-tee beams for bridge 2
have an overall span length of 110
ft, which according to the Precast/
Prestressed Concrete Institute, is one
of the longest spans for a bridge
Precast concrete beams for the Fairmont Bridge Replacement were transported to the
site by truck.
carrying Cooper E-80 train loads in
New England. To achieve the long
span, the bulb tees were spaced at
4 ft on center, using four beams
connected laterally with concrete
diaphragms to support each track
during construction.
and moved it two-thirds of the way
over the river. The second crane, on
the opposite side, connected the sling
on the far end in midair to transfer
partial beam load to itself.
____________
A 10- to 12-in.-thick, cast-in-place
reinforced concrete deck was placed
o n t h e b e a m s . R a i s e d c o n c re t e
walkways cantilevered beyond the
exterior beam to contain the ballast
a n d tra cks . The new out-to-out
concrete deck widths are 37 and 36 ft
for bridges 1 and 2, respectively.
Aboud Alzaim is senior vice president
in charge of Louis Berger Group Inc.’s
northeast transportation division.
Malek Al-Khatib serves as associate vice
president and Daniel Deng is a structures
and facilities engineering manager, both
within the northeast transportation
division of the Louis Berger Group Inc., in
Needham, Mass.
The beams were fabricated in
Pennsylvania and transported to the
sites. Two cranes located behind
opposite abutments were used to lift
each beam. One crane lifted the beam
Fo r a d d i t i o n a l p h o t o g r a p h s o r
Current Issue.
SATUS CREEK BRIDGE
Curved, tilted, precast concrete box girders key to replacement project
by Michael Bressan and Paul D.
Kinderman, Washington State
Department of Transportation
Curved trapezoidal girders were used for the Satus Creek Bridge in south central Washington state. All photos: Washington State
Department of Transportation Visual Engineering Resource Group.
Satus Creek Bridge is located 25 miles
southwest from Toppenish, Wash.,
where U.S. 97 crosses Satus Creek.
It was constructed as part of a $13.4
million project completed in the first
part of 2013. It replaced an old, loadrestricted timber bridge built in 1942.
Washington State Department of
Transportation (WSDOT) designed this
new, resilient structure to correct design
deficiencies with the old timber bridge
including vehicular impact and seismic
resistance. Several unique features are
implemented in the design including
horizontally curved and spliced precast
concrete girders.
Structural Design
The Satus Creek Bridge is a 180-ft-long,
simple-span bridge. This long, singlespan bridge was necessary to satisfy
environmental constraints to cross the
wide section of the creek. The 7.5-in.thick bridge deck is comprised of
conventional, cast-in-place concrete.
The shallow foundation also consists of
conventional, cast-in-place concrete that
is 18 ft tall.
profile
The superstructure is comprised of three
open, precast concrete box girders,
which are horizontally curved and
tilted to match the 8% cross slope of
the bridge. The girders are the WSDOT
U78PTG5 series. The “78” indicates the
height of the webs in inches and the
“5” identifies the width of the bottom
flange in feet. Bottom flange and
web thicknesses are 6 in. and 10 in.,
respectively.
the span capability, which eliminated
the need for an intermediate pier.
This was a great cost savings and it
satisfied WSDOT’s environmental
constraints. Another added benefit
of the spliced girders was reduced
shipping costs. The precast concrete
segments are easier to handle and
more shipping routes were available
to the precaster due to shorter and
lighter components.
To achieve this long, simple span across
Satus Creek, each girder line consists
of three precast concrete girder
segments. Falsework towers were used
to temporarily support the segments
while the deck was cast and subsequent
to assembly of the splice sections. Each
web has three post-tensioning tendons
comprised of nineteen, 0.6-in.-diameter
strands with a total estimated jacking
force of 2505 kips per web. After posttensioning was applied, the temporary
falsework towers were removed.
Each girder segment was precast with
a 1290 ft radius in the horizontal
plane. In the bridge special provisions,
WSDOT allowed the precaster to
chord the girder segments at 20-ft
intervals to achieve the prescribed
horizontal radius. This construction
method would have facilitated the
use of conventional, less-expensive,
flat formwork panels that are readily
available. For this particular project,
the precaster was able to build a form
to the prescribed radius, achieving a
smooth face for each girder segment
and a smoother transition between
segments at time of assembly.
Splicing the segments in the field after
the deck was made composite increased
SATUS CREEK BRIDGE / TOPPENISH, WASHINGTON
BRIDGE DESIGN ENGINEER AND ARCHITECT: Washington State Department of Transportation, Olympia, Wash.
GENERAL CONTRACTOR: Franklin Pacific Construction Company, Seattle, Wash.
PRECASTER: Concrete Technology Corporation, Tacoma, Wash.—a PCI-certified producer
POST-TENSIONING CONTRACTOR: Schwager Davis Inc., San Jose, Calif.
Thermal Integrity Profiler (TIP)
The Heat Is On.
Winner of
the DFI 2013
C. William
Bermingham
Award for
Innovation
Shape, quality, cage alignment and
concrete cover of drilled shafts.
Winner of
the 2013
CIF/CURT NOVA
Award for
Innovation
Two options for data acquisition:
Probes or Thermal Wire® cables.
TIP testing goes fast and is done
soon after casting, so construction
can move on.
Close up of the splice between precast
concrete girder segments.
The girders were analyzed as straight
segments because:
• the girders are concentric,
• the bearings are not skewed,
• the arc span divided by the girder
radius (the central angle) is less
than 12 degrees as permitted by
AASHTO design requirements, and
• the girder depth is less than the
width of the box at mid-depth.
www.foundations.cc
[email protected]
www.pile.com/tip
[email protected]
These considerations simplified the
analysis of the structure. Three different
software packages were used to design
the girders: a proprietary software,
PG-Splice (developed by WSDOT), and
PG-Super (developed by WSDOT). The
proprietary software and PG-Splice
were both used to verify the validity
of each other’s results. Both the
proprietary software and PG-Splice
were utilized to design the main posttensioning tendons to resist self-weight,
superimposed dead loads, live loads,
and temperature gradients.
PG-Super was utilized to design the
prestressing strands of the individual
segments to withstand the stresses
induced during the temporary
Falsework towers were used to
temporarily support the segments while
the deck was cast and subsequent to
assembly of the splice sections.
WASHINGTON STATE DEPARTMENT OF TRANSPORTATION, OWNER
PROJECT DESCRIPTION: An 180-ft-long, simple-span bridge with horizontally curved, tilted, spliced precast concrete box girders and a
1290-ft-radius horizontal alignment
STRUCTURAL COMPONENTS: WSDOT U78PTG5 precast concrete tub girders with a 28-day design compressive strength of 8.5 ksi and a cast-inplace concrete deck and foundation
construction stage, which included
loads from the deck, diaphragms, and
concrete formwork. Additionally, the
prestressing strand design was checked
to ensure the girders remained within
allowable stress limits during shipping
and handling of the girder segments
prior to assembly.
The post-tensioning tendon paths are
parabolic and the post-tensioning losses
included:
• f r i c t i o n b e t w e e n t h e p o s t tensioning steel and the ducts,
• duct misalignment,
• anchorage slip,
• concrete elastic shortening,
• concrete creep and shrinkage,
• relaxation of post-tensioning steel,
and
• stressing sequence.
Earth-tone oxidizing concrete color
blends with south-central Washington
colors.
Concrete colors and textures complement
natural riprap slope protection.
For this particular project, an important
aspect in calculating friction losses was
the correction for the effects caused by
the built-in horizontal curvature. These
friction losses introduced by the horizontal
curvature were small due to the fairly large
radius. Yet the designer could not ignore
their effects.
Another interesting design facet for the
Satus Creek Bridge is the consideration of
Curved trapezoidal girders showing closure concrete placements and diaphragms.
out-of-plane and in-plane forces caused
by the tendons placed along the webs.
These forces are caused by the spreading
of the strands within the post-tensioning
ducts and by the horizontal and vertical
curvatures assumed by the post-tensioning
tendons due to the bridge geometry.
Small, out-of-plane and in-plane forces
may be resisted by the concrete in shear.
However, in this project, the addition of
stirrups around the post-tensioning ducts
along the whole length of the girders
provides the necessary resistance to
withstand these forces.
and girders are colored and textured for
contrast.
Due to the tremendous forces involved,
special attention was given to the end
blocks. Two areas of interest were
considered: the local zone and the general
zone. The local zone is designed to
resist the forces introduced by the posttensioning anchors. The general zone is
designed to resist the forces introduced
by the jacking forces and the stressing
sequence of the post-tensioning tendons.
It is not uncommon for end blocks to
become fairly large to accommodate the
post-tensioning anchors and to provide
adequate reinforcement to withstand the
forces applied in the general zone.
Lessons Learned
Architectural Design
This bridge is set in the rural, semi-arid
region of south-central Washington
state. Except for the creek valley, the
area is treeless. Native grasses, sage
brush, and basalt rock create colors
ranging from golden yellows to reddish
browns. The bridge finishes respond to
these textures and colors. The abutments
and retaining walls are made of castin-place concrete with fractured basalt
formliners, while the hardened surface
is colored with a natural oxidizing agent
to blend with the terrain. The barrier
The use of curved concrete girders
transforms the aesthetic possibilities
of precast concrete bridges. Although
straight girder sections can be placed on
horizontal alignments, there are limits
to deck overhangs. These overhangs
are invariably changing along the span,
creating visual discord. However, with
the use of curved girders, the horizontal
radius can be less and the deck overhang
remains constant.
The Satus Creek Bridge is the first
horizontally curved, precast, post-tensioned
concrete girder bridge to be built in the
state of Washington. It is a cost-effective,
durable, and resilient structure that
is aesthetically pleasing to the eye while
satisfying the geometric and environmental
constraints of the site.
Satus Creek Bridge was a testing ground
for the WSDOT Bridge and Structures
Office. The WSDOT team did not encounter
significant issues during the design and
construction phases of this project. Overall,
horizontally curved post-tensioned spliced
girders were found to be innovative and
cost-effective, while allowing WSDOT to
maintain a high level of safety and resiliency
in the state’s highway bridges.
____________
Michael Bressan is a bridge engineer 4 and
Paul D. Kinderman is a bridge architect
with the Washington State Department of
Transportation in Olympia, Wash.
For additional photographs or information
on this or other projects, visit www.
aspirebridge.org and open Current Issue.
DELIVERING SUPPORT & INGENUITY
Local Presence - Global Competence
www.dsiamerica.com
Bolingbrook, Illinois
Phone (630) 739-1100
Mansfield, Texas
Phone (817) 473-6161
Tucker, Georgia
Phone (770) 491-3790
Pompano Beach, Florida
Phone (954) 532-1326
Structural Repair and Strengthening
Phone (630) 972-7513
Long Beach, California
Phone (562) 531-6161
Toughkenamon, Pennsylvania
Phone (610) 268-2221
[email protected]
140204_aspire_117-8_117.indd 1
25.02.2014 15:17:50
Congratulations to the...
2013 ASBI Bridge Award
of Excellence — Winners
South Norfolk Jordan Bridge, Virginia
American Segmental Bridge Institute
The Charles W. Cullen Bridge Over the Indian River Inlet, Delaware
Veterans Memorial Bridge Replacement, Maine
Miami Intermodal Center – Earlington Heights Connector, Florida
New Cross-Border Combined Bridge Over the Danube River, Romania
Foothills Parkway Bridge Two, Tennessee
Promoting Segmental Bridge Construction
in the United States, Canada and Mexico
Remember these dates....
April 14-15
2014 Grouting Certification
T R A I N I N G
J.J. Pickle Research Campus
University of Texas, Austin
October 27-28
2014 Annual ASBI
CONVENTION
Hartford Marriott Downtown and
Connecticut Convention Center
For Membership Information or For Further Details, Visit www.asbi-assoc.org
14060_ASBI_ASPIRE_Spring_2014_ad_1.indd 1
11/6/13 2:48 PM
ASPIRE, Winter 2013 | 27
PROJECT
MONTLAKE TRIANGLE
PEDESTRIAN BRIDGE
Curved, post-tensioned structure links Seattle campus to downtown
by Claudio Osses and Richard Patterson, Buckland & Taylor, and Orin Brown and Huanzi Wang, AECOM
The Montlake Triangle Pedestrian (MTP)
Bridge is a highly-curved, 427-ft-long,
cast-in-place (CIP), post-tensioned
concrete pedestrian bridge spanning
over Montlake Boulevard between
the Sound Transit light-rail station and
the University of Washington (UW)
campus in Seattle, Wash. A number
of challenges to bridge design and
c o n s t r u c t i o n w e re p re s e n t e d b y
the unique geometry, curved post-
tensioning, dissimilar foundations,
and the need to interface with several
structures and utilities, both new and
existing. It is anticipated that this daring
bridge will become a landmark for both
the UW and the city of Seattle.
Project Overview
The MTP Bridge was designed and
constructed as part of Sound Transit’s
University Link project to extend light-
rail from downtown Seattle to the UW
campus. The new station is located on
the east side of Montlake Boulevard
directly across from the UW Triangle
area. This Triangle area is being
revitalized by the UW, enhancing the
view of Mount Rainer from campus
with new landscaping and improving
pedestrian and bicycle access. The
Headhouse is a building structure that
forms the above-ground portion of the
Montlake Triangle Project. Rendering: LMN.
profile
MONTLAKE TRIANGLE PEDESTRIAN BRIDGE / SEATTLE, WASHINGTON
BRIDGE DESIGN ENGINEER: AECOM, Seattle, Wash.
ARCHITECT: LMN, Seattle, Wash.
PRIME CONTRACTOR: Hoffmann Construction, Seattle, Wash.
POST-TENSIONING CONTRACTOR: Schwager Davis Inc., San Jose, Calif.
Montlake Triangle Pedestrian Bridge project. Photo: Sound Transit.
new, underground light-rail station. The
MTP Bridge provides a direct connection
for pedestrians and bicyclists between
the Triangle area and the Headhouse.
Bridge Layout
The layout of the bridge consists of two
horizontally curved alignments:
• The northeast outside curve
(M1-line) with a 152-ft radius
• T h e s o u t h w e s t i n s i d e c u r v e
(M2-line) with a 94-ft radius
Both alignments begin with pier 1
on the UW Triangle and curve to the
right with span 2 of both alignments
crossing over Montlake Boulevard. The
M1-line has a deck width of 16 ft and
consists of five spans with lengths of
55, 131, 76, 100, and 65 ft, ending
with a 5-ft cantilever past pier 6E
inside the Headhouse. The M2-line has
a deck width of 14 ft and consists of
eight spans with lengths of 49, 115,
40, 47, 30, 36, 36, and 36 ft, ending at
where the two lines meet. The M2-line
beyond the span 4W hinge is a cast-inplace, reinforced concrete slab girder
with a minimum depth of 2 ft and a
cross-sectional shape that matches the
pier 9W as a bicycle access ramp along
the east side of Montlake Boulevard.
From the middle of span 1 to the
middle of span 2, the bridge decks of
the two alignments merge into one,
making the horizontal geometry
resemble a highly curved “X”
in plan view, including a forked
superstructure at each end of
the two spans.
In-span hinges were added to
the bridge to divide the bridge
into three more-regular bridge
segments, which improved
the overall static and seismic
bridge behavior and simplified
the analysis and design. The
entire M1-line and the M2-line
up to the span 4W hinge are
5-ft-deep, cast-in-place, posttensioned, concrete single-cell
box girders, which become
a three cell box in the area
FRAME 1
PIER NO.
IN-SPAN HINGE
3
2
4E
2
1
M1-LINE
1
M2-LINE
3
FRAME 2
FRAME 1
4W
IN-SPAN HINGE
5W
5E
6W
BICYCLE
RAMP
7W
6E
8W
9W
Bridge layout. Drawing: AECOM.
SOUND TRANSIT, OWNER
REINFORCEMENT SUPPLIER: Harris Rebar, Tacoma, Wash.
FORMWORK: Peri Formwork Systems Inc., Woodland, Wash.
PROJECT DESCRIPTION: 427-ft-long by 12- to 35-ft-wide multispan, curved, 5-ft-deep, cast-in-place, post-tensioned concrete box girder bridge
founded on drilled shafts, spread footings, and an underground light-rail station
Solid Box
Solid Box
M1 Box
M2 Box
Framing plan. Drawing: AECOM. Photo: Sound Transit.
overhangs of the box girder. Beyond
pier 9W there is a 16-in.-thick approach
slab resting on soil sandwiched between
two mechanically stabilized earth walls
that are about 60 ft long.
Vertical design constraints required
the bridge to meet stormwater runoff
requirements and match predetermined
elevations for three sets of stairs, an
escalator, three elevators, temporary and
permanent vertical clearances for traffic,
and permanent clearances for pedestrians
and bicycles. The Headhouse escalator 1
and stair 1 are side-by-side structures that
are supported by, and join the end of, the
M1-line bridge girder near pier 6E.
Superstructure
The uneven span arrangement (end-span
to main-span length ratio of 0.4) required
the use of special design techniques,
including the use of a vertical tie rod,
a hinge, and mass concrete at selected
end-span box cells to control live load
uplift reactions at pier and in-span hinge
bearings.
Web ties
Duct tie
Duct-tie and web-tie reinforcement.
Drawing and Photo: AECOM.
Typically, post-tensioning is avoided in
highly curved bridges due to difficulties
associated with the large out-of-plane
forces induced. However, post-tensioning
was chosen for this bridge because it
allowed a shallow section that met the
vertical clearance requirements and
produced a high-level architectural finish
without the normal cracking associated
with typical reinforced concrete bridges.
In order to better resist the girder torsion
due to gravity loads and the lateral
bending due to horizontally curved
post-tensioning, the two box girder
alignments were transversely connected
by a soffit slab. This soffit slab is located
where the decks merge together and
by integral bent cap crossbeams at piers
1 and 3. The soffit slab between the
box girders where the decks converge is
recessed 9 in. upward from the soffit of
the box girders for aesthetic reasons.
With such a complex geometry, simplified
straight line models are incapable
of capturing important aspects of the
structural behavior of the bridge such as
the effect of the post-tensioning on the
global bridge response and the concrete
stress and load distribution across the
bridge section. A more sophisticated
three-dimensional, structural, finiteelement model was used to capture
the static and dynamic behavior of the
bridge.
The tight horizontal bridge curvature
required special post-tensioning
analysis, detailing, and construction.
Post-tensioning a structure with such a
tight horizontal curve produces variable
concrete stresses across the bridge
section and causes transverse tension
in the slabs between the webs and
undesirable torsional effects if the tendon
forces are not distributed properly. Using
prestressing forces at each web that were
roughly proportional to the span length
of each web minimized these undesirable
effects. Additionally, a construction
analysis by stages was used to determine
the optimal jacking sequence to minimize
any undesirable post-tensioning effects.
AESTHETICS
COMMENTARY
by Frederick Gottemoeller
This bridge reminds me of the old television advertisements for Perdue chickens. In those advertisements, Frank Perdue
would talk at length about chickens, and then end his spiel with, “It takes a tough man to grow a tender chicken.” This
bridge demonstrates that it takes excellent engineering to make a complicated bridge look so simple. And that’s important
because this bridge’s aesthetic appeal is based on the simplicity with which its complex geometry is addressed. The bridge
is an interesting shape, and it is unencumbered by pier caps, straddle bents, expansion joints, or any of the other details
that may be distracting.
The girders are relatively shallow, giving the pedestrian areas under the bridge a feeling of spaciousness. They curve to
follow the curve of the deck, creating a generous and constant-width overhang that contributes a consistent shadow line, making the girders
seem even thinner. The smooth undersides of the girders provide a clean and light-colored ceiling for this outdoor space; space that pedestrians and bicyclists can occupy without worrying about birds and debris overhead.
The circular piers have no axes or planes that would conflict with the curves of the girders floating above. They also allow the myriad paths
of pedestrians and bicycles to flow past them with a minimum of interference. The straightforward railing allows the overall geometry of the
bridge to dominate, creating no secondary rhythms or panelization that would distract. The light poles serve their function without attracting
the eye away from the bridge itself.
Once the Sound Transit University link is in service, the Montlake Triangle will be filled with the activity of pedestrians, bicyclists, and transit
riders. This bridge will provide a dignified and memorable setting for all of them.
______________
Frederick Gottemoeller is an engineer and architect, who specializes in the aesthetic aspects of bridges and highways. He is the author of
Bridgescape, a reference book on aesthetics and was deputy administrator of the Maryland State Highway Administration.
5’–0”
7”
VARIES (30’–0” MIN)
Typical section at frame 1. Rendering: AECOM.
The girder web stirrups also needed
to be designed to resist vertical shear
and lateral web bending caused by the
horizontally curved post-tensioning.
The strut-and-tie method was used to
analyze and design the duct-tie and webtie reinforcement to resist the local outof-plane lateral post-tensioning forces.
Special attention had to be paid to the
placement of the duct-tie and web-tie
reinforcement during construction, as
this reinforcement was critical in resisting
the post-tensioning, out-of-plane forces.
Two measures incorporated to enhance
the durability of the bridge were the use
of epoxy-coated reinforcement in the
7-in.-thick deck, and the use of highdensity polyethylene corrugated ducts for
the post-tensioning tendons.
Substructure
The girders are integral with 4-ft
-diameter columns at piers 2, 3, 4E,
and 4W, and with 2-ft 6-in.-diameter
columns at piers 5W through 8W. The
girders are supported on expansion
bearings at piers 1, 5E, 6E, 9W, and at
the span 3E and 4W hinges.
Another unique feature of this bridge
is that the foundations are dissimilar
between piers. Pier 1 is founded on
two, 4-ft-diameter drilled shafts, one
under the centerline of each box
girder alignment. Piers 2 and 3 are
founded on two-column combined
spread footings 4 ft 6 in. thick. Pier
4E is founded on top of a large roof
beam within the underground lightrail station. Piers 5E and 6E are part
of the Headhouse building frame. Pier
4W is supported on a single-column
spread footing 4 ft 6 in. thick. Piers
5W through 8W (supporting the bicycle
ramp) are all founded on single-column
spread footings 2 ft 6 in. thick. Pier
9W is an abutment bearing wall with
wingwalls, which all bear on a spread
footing that is 1 ft 9 in. thick.
Because piers 4E, 5E, and 6E are all
founded on the building frame of either
the Headhouse or the station roof, the
bridge engineers provided all design loads
and displacements to the station designer,
and included the Headhouse frame in the
bridge analysis model. A special seismic
design criterion was developed to satisfy
bridge (displacement based) and building
(force based) code philosophies for the
spans supported by the Headhouse.
Final Remarks
The design of the MTP Bridge has pushed
the limits for the use of post-tensioning in
highly curved bridges, demonstrating that
with the proper analysis and detailing,
durable and low maintenance posttensioned concrete bridges can be used
for bridges.
____________
Claudio Osses is a bridge engineer and
Richard Patterson is the Washington
practice lead with Buckland & Taylor in
Seattle, Wash. Both Osses and Patterson
were formerly with AECOM. Orin Brown
and Huanzi Wang are bridge engineers
with AECOM in Sacramento and Oakland,
Calif., respectively.
For additional photographs or
Current Issue.
CALL FOR ENTRIES
2014 CONCRETE BRIDGE AWARDS COMPETITION
The Portland Cement Association invites entries for its Fourteenth Biennial Bridge
Awards Competition to recognize excellence in design and construction of concrete bridges.
E LIG I BI LIT Y: Eligible structures for the 2014 competition must have
been essentially completed between October 2011 and September 2013,
and must be located within the United States or Canada.
B R I DG E C R ITE R IA: All types of bridges—highway, rail, transit,
pedestrian, and wildlife crossing—in which the basic structural system
is concrete are eligible. Entries are equally encouraged for cast-in-place
or precast concrete bridges with short, medium, or long spans. Newly
constructed, reconstructed, or widened structures qualify for the
competition.
WH O M AY E NTE R : Any organization, public or private, may enter
and may submit multiple entries. Note that written evidence of the
agreement by the owner agency to the submission of each entry shall be
included with each entry.
RU LE S O F E NTRY:
See online entry form at www.cement.org
Entry fee of $250.00 per submission.
Deadline: Entries are due May 30, 2014.
J U DG I N G : Selection of winners will be made by a jury of distinguished
professionals. Awards will be made in recognition of creativity and skillfulness in the structural, functional, aesthetic, sustainable, and economic
design of concrete bridges. Consideration will also be given for innovative construction methods, including accelerated bridge construction.
AWAR DS: Multiple Awards of Excellence will reflect the diverse ways
concrete is used in bridges. Each award will consist of a commemorative
plaque to be presented at the American Concrete Institute’s Fall
Convention to be held in Washington, DC on October 26-30, 2014.
Post-tensioning makes possible
the cost-effective construction
of high-quality bridges over a
wide range of site conditions
and design requirements.
Bridge structures constructed
using post-tensioning have high
intrinsic durability and are able
to be built quickly with minimal
impact on the natural and
human environment.
PTI offers technical guidance, training and certification programs, and events to enhance your next bridge project.
• Level 1 & 2 Bonded PT Field Specialist
Certification
• PTI M50.3-12: Guide Specification for
Grouted Post-Tensioning
• 2014 PTI Convention, May 4-6,
in Norfolk, VA
• PTI DC45.1-12: Recommendations for
Stay-Cable Design, Testing and Installation
• PTI M55.1-12: Specification for
Grouting of PT Structures
www.Post-Tensioning.org
MASSENA BRIDGE
L AT E R A L S L I D E R E P L AC E M E N T
This photo shows the finished Massena Bridge after the lateral slide replacement. All photos: Iowa Department of Transportation.
Improving safety and reducing congestion in the construction
zone were two primary factors that motivated the Iowa
Department of Transportation (Iowa DOT) to develop a
policy for accelerated bridge construction (ABC). Although
several ABC projects had been completed in Iowa prior to the
policy implementation in 2012, the ABC policy allowed for a
systematic approach to selecting ABC projects.
bridge slide design depends on the means and methods
chosen by the contractor, the design team chose to show
one feasible slide concept and associated details in the
plans. Components for the slide that were anticipated to be
permanently incorporated into the final structure included
the slide shoe, jacking pockets, bearing pads, and solid end
diaphragms.
As part of the ABC policy implementation, the Iowa DOT
selected bridge sites across the state for the purpose of
demonstrating various ABC methods and developing
workforce expertise. The Massena Bridge site was identified for
a lateral slide. One of the advantages of this method is the use
of traditional construction methods.
The solid end diaphragm details were different than
those in a traditional design. The end diaphragm had to
accommodate jacking pockets, high-strength threaded
rods, and anchorages used to push or pull the bridge
superstructure.
Massena Design
For design of the sliding shoe and bearing pads, the
coefficient of friction was needed for the interaction
between the pad and specified stainless steel. The Iowa DOT
commissioned laboratory testing by Iowa State University
(ISU) of a full-scale mock-up of the slide shoe and bearing
pads. The tests were performed in both lubricated and nonlubricated conditions with the lubricant being common dish
washing soap. Test results indicated that the suggested 10%
coefficient of friction for design was reasonable.
Constructed in 1930, the original bridge over a small stream
in Cass County near Massena, Iowa, had been designated
as structurally deficient with a sufficiency rating of 38, load
posted for one truck at a time, and was in need of major
rehabilitation or replacement. A 120-ft-long by 44-ft-wide
prestressed concrete, single-span structure was chosen to
replace the existing 40-ft-long by 30-ft-wide steel beam bridge.
With a focus on building internal ABC design expertise, the
preliminary and final designs were performed by Iowa DOT
engineers. But because this was the first design for a lateral
slide in Iowa, a design firm with significant experience in lateral
slide was retained to conduct a design-constructability review.
The bridge superstructure consists of six 45-in.-deep,
prestressed concrete bulb-tee beams with specified concrete
compressive strength of 9.0 ksi at 28 days and an 8-in.thick, cast-in-place concrete deck. While much of a lateral
Laboratory Confirmation
Iowa DOT had previous ABC experience and research results
with precast concrete abutment footings founded on driven
HP10 piling. However, an HP14x117 was selected to meet
the design and constructability requirements of this project.
Extrapolating the original research data to a pile about
twice as large was not felt to be appropriate and so ISU
was commissioned to do laboratory testing of the new
precast concrete abutment footing to pile pocket detail. The
laboratory testing confirmed the design capacity of the new
A C C E L E R AT E D B R I D G E C O N S T R U C T I O N
by Ahmad Abu-Hawash and James Nelson, Iowa Department of Transportation
The lateral bridge slide
ABC methodology provided a
net savings of about $100,000
versus the traditional
construction methodology.
minimal traffic restrictions. This work included
seeding, revetment, and clean-up. A maximum of
15 working days was allowed for this phase.
Four local contractors participated in the April 16,
2013, letting with the bids ranging from $1.3 to
$1.6 million. The calculated unit cost of $122/ft2
of deck area—30% more than typical non-ABC
projects for this bridge type in Iowa—is considered
very reasonable based on past Iowa ABC projects.
Furthermore, this direct construction cost premium
is more than offset by the indirect user costs.
larger connection details.
Bidding and Contracting
With ABC in mind, the construction contract had three phases.
• Phase 1: construction of the replacement bridge
superstructure on temporary supports. Constructing
off alignment allowed the contractor to work with no
working days being charged.
• Phase 2: the ABC period (called the critical closure).
The contractor was allowed a maximum of nine days of
road closure to remove the old structure, erect the new
bridge in its final position, and restore traffic operations.
A $10,000 per day incentive/disincentive clause was
specified for this phase.
• Phase 3: miscellaneous work performed with no or
The new bridge superstructure nears
completion. A jacking frame has been
installed for a test roll.
User costs for the traditional construction
methodology, which would have detoured
traffic for the duration of the construction, were
estimated at over $400,000. Indirect user costs—
such as the value of people’s time, safety, and lost
local business due to inconvenience—were not
included. If the simple user costs are factored into the cost of
the project, the lateral bridge slide ABC methodology provided
a net savings of about $100,000 versus the traditional
construction methodology.
Contractor Modifications
In lieu of the precast concrete abutment footings that were
specified in the contract documents, the contractor requested
to construct the abutment footings using the traditional castin-place concrete method. With the understanding that the
contractor is still limited to the same nine-day ABC period, Iowa
DOT did not object to the request for change. The contractor
utilized a concrete mixture that achieved high early strength with
typical insulation. The maturity method was used to verify the
concrete strength.
Preparing the high-strength threaded
rods to pull the prefabricated bridge
superstructure into position.
The jacking frame for pulling the
prefabricated bridge superstructure into
position.
The contractor also proposed to change the sliding system
from the stainless steel sliding shoe and bearing pads to heavy
duty rollers. The contractor had previously rolled a railroad
bridge and already owned several rollers. This alternative was
anticipated and allowable by the specifications. It required
minor plan changes to delete the stainless steel from the
sliding shoe and delete the pads from the bearings. A few
weeks prior to the bridge slide, a test move was conducted
successfully by rolling the bridge in the opposite direction of
the actual move to verify the system operation.
Lifting the bridge superstructure with pancake jacks to remove
the rollers.
Constructing and Opening
The contractor began the critical closure on Friday, September
27, by implementing the roadway detour and beginning
demolition of the existing bridge. By the evening of Monday,
September 30, the contractor was ready to move the
prefabricated bridge superstructure commencing the move
at about 7:30 p.m. The move was completed by 2:00 a.m.
the next morning, taking about 6½ hours to complete. Gage
pressure readings on the jacks were monitored along with
the relative distance of travel of both ends of the bridge. The
equivalent coefficient of friction typically varied from 2.5 to
5% with a brief period when the gage pressures correlated to
an equivalent coefficient of friction of 13% due to binding or
racking of the system.
Following the prefabricated concrete bridge superstructure
move, there were many additional work items on the critical
path including precast concrete wingwall installation, subdrain
installation, backfilling, approach pavement placement,
longitudinal grooving, painting, and guardrail installation.
The contractor completed these activities expeditiously and
reopened the roadway to traffic on Sunday, October 6.
This project was considered to be a successful demonstration
of a lateral bridge slide. Both the contactor and Iowa DOT
achieved the desired critical closure schedule with quality
construction. Even in a successful project, there can be lessons
to be learned and room for improvement on future projects.
As a standard practice on ABC projects, the Iowa DOT held
a post-construction review meeting to gather feedback
from both the DOT staff who worked on the project, the
contractor, and the contractor’s engineer. Notes from the
post-construction review can be found on the project website
(http://www.iowadot.gov/MassenaBridge/index.html).
Roller in guide channel for rolling the prefabricated bridge
superstructure.
this ABC methodology again where appropriate. Currently,
ABC design concepts for several bridge replacement projects
in Iowa are being developed with serious considerations
given to the lateral slide method.
__________________
Ahmad Abu-Hawash is the chief structural engineer and James
Nelson is a design section manager for the Iowa Department of
Transportation in Ames, Iowa.
Team members for the Massena Bridge included Iowa
Department of Transportation, bridge design engineer, Ames,
Iowa; Herberger Construction Co., prime contractor, Indianola,
Iowa; and Cretex Concrete Products, a PCI-certified precaster,
Iowa Falls, Iowa.
Based on the success of the Massena Lateral Slide Bridge
Replacement project, the Iowa DOT would not hesitate to use
A C C E L E R AT E D B R I D G E C O N S T R U C T I O N
The switch to cast-in-place for the abutment footing
eliminated the risk of the precast concrete footing pile pockets
not fitting over the driven H-pile deep foundation. Pile driving
tolerances were 3 in. in any direction from the intended center.
Past ABC projects had shown this tolerance to be achievable
with the use of a rigid template and contractor care. The
contractor also felt that curing of the entire footing was
preferable over the curing of just the pile pocket concrete. The
larger mass of concrete generates more heat of hydration for
faster strength gain versus the smaller mass of concrete of just
the pile pockets alone.
F H WA
The Long-Term
Bridge Performance
Program
by Jorge E. Pagán-Ortiz and Hamid Ghasemi, Federal Highway Administration; M. Myint Lwin,
formerly with Federal Highway Administration; and Ali Maher, Rutgers: The State University of New Jersey
Virginia Center for Transportation Innovation
and Research along with the University of
Virginia and Virginia Tech; Bridge Diagnostic
Inc.; and the technology provider, Advitam.
The research team receives regular
input from advisory groups, such as the
American Association of State Highway and
Transportation Officials, state departments
of transportation and the Transportation
Research Board, to ensure that the research
products are of value to the stakeholders.
Developmental Phase
Various non-destructive evaluation technologies (impact echo, ground-penetrating radar, electrical resistivity,
moisture scan, and half-cell potential) were deployed in the first pilot bridge to kick-off the Long-Term Bridge
Performance Program. Photo: Federal Highway Administration.
I
n the Safe, Accountable, Flexible, Efficient
Transportation Equity Act: A Legacy for
Users (SAFETEA-LU), the U.S. Congress
directed the Secretary of the U.S. Department
of Transportation to establish a 20-year study,
develop grants, and enter into cooperative
agreements and contracts to
• monitor, material test, and evaluate test
bridges;
• analyze the data obtained; and
• prepare products to fulfill study
objectives and meet future bridge
technology needs.
A c c o r d i n g l y, t h e Fe d e r a l H i g h wa y
Administration (FHWA) initiated a multifaceted
research study in 2008 that is strategic in nature
with short- and long-term goals. Under this
study, referred to as the Long-Term Bridge
Performance (LTBP) Program, critical aspects
of bridge performance are being examined
to better understand the performance of
existing and new bridges. The funding for the
program has continued through MAP 21-The
Moving Ahead for Progress in the 21st Century
Act, which is a funding and authorization
bill to govern United States federal surface
transportation spending.
The Research Team
The LTBP Program’s research team consists
of a coordinated, collaborative, multiinstitutional, and multi-disciplinary group
of professionals in government, academia,
and industry. FHWA is the lead agency. The
primary contractor is Rutgers University,
working in par tnership with Parsons
Brinkerhoff; the Utah State University; the
In the developmental phase, researchers
began to synthesize existing information
on bridge performance and identified
performance issues facing bridge owners
in the United States. Based on available
resources, researchers developed a short list
of high-priority bridge performance topics to
be immediately considered for the long-term
data collection phase of the LTBP Program.
These topics include performance of treated
and untreated concrete bridge decks, joints
and bearings, coatings for steel superstructure
elements, and encapsulated prestressing
strand and post-tensioning tendons.
After identifying a prioritized list of
questions to be answered, the following steps
were taken:
1. Examine the questions to identify the
potential for data needs.
2. Design experiments to identify the
specific data to be collected.
3. D e t e r m i n e t h e fe a s i b i l i t y a n d
economics of collecting reliable and
quantitative data both from legacy
sources and from LTBP Program’s
field monitoring activities.
4. Sort, store, and analyze data through
the LTBP Program data portal to
address the question from step 1 and
close the knowledge creation loop.
Demonstration of the RABIT TM bridge deck
assessment tool at the U.S. 15 Bridge over I-66 in
Haymarket, Va. Photo: Rutgers University.
Robot components of the RABIT TM bridge deck assessment tool expedites field data collection. Photo: Rutgers
University.
Protocols for Data
Protocols for data sampling and
collection using inspection techniques and
instrumentation, and data quality assurance
to carry out these functions were developed
to ensure consistent quality. The protocols
were documented sufficiently so that any
interested party can use them to collect and
analyze data. This also allows for proper
comparison with data already gathered by
the LTBP Program. These protocols are living
documents and will be updated frequently.
Sampling Methodology
T h e LT B P P r o g r a m ’s s a m p l i n g
methodology, referred to as the reference
bridge/cluster bridges approach, concentrates
on small geographic areas and contiguous
sections of highways known as corridors.
Briefly, this concept involves identifying small
groups of similar bridges, or clusters, from
FHWA’s National Bridge Inventory (NBI)
database and studying one or more of the
high-priority bridge performance topics
using data collected from those bridges. The
number of any one cluster will vary, but
usually will be about 75 bridges.
Two to four of the bridges within each
cluster will be selected as reference bridges
and will undergo an optimum periodic
inspection and monitoring using visual
inspection supplemented with automated
bridge deck non-destructive evaluation
(NDE), and fiber-optic-based weigh-inmotion systems. The supporting cluster of
bridges will only undergo detailed visual
inspection and limited NDE or physical
testing for reference bridge comparison to
ascertain consistency.
Data Management
To manage data collected through the
LTBP Program, it was necessary to develop
an information technology infrastructure for
storing, analyzing, updating, and accessing
multiple data models with appropriate security
considerations that could be used by a variety of
stakeholders. The LTBP Program’s Bridge Portal
was developed to handle this requirement.
Data Collection Phase
The LTBP Program’s long-term data
collection phase began in March 2013 in the
mid-Atlantic region and will move to other
regions of the United States in 2014. The
expectation is that up to 1000 bridges will
undergo detailed testing, periodic evaluation,
and monitoring over the next 20 years. Over
90 test protocols have been developed and are
currently being deployed to standardize data
collection efforts.
Finally, an automated data collection tool,
the RABIT TM bridge deck assessment tool, a
product of the LTBP Program, is being deployed
to expedite field data collection for the study.
The photo on the previous page shows the
demonstration of the RABIT TM bridge deck
assessment tool for FHWA’s administrator, Victor
Mendez, on the U.S. 15 Bridge over I-66 in
Haymarket, Va.
Moving forward with data collection,
researchers will continue to develop refined
deterioration and life-cycle cost models and a
data-driven bridge condition index. FHWA will
continue its outreach efforts to make available
a suite of best practices involving bridge
design, construction, inspection, maintenance,
preservation, and monitoring to assist bridge
owners in making better management decisions.
EDITOR’S NOTE
For additional information, please visit
FHWA’s internet web page at http://
w w w. f h w a . d o t . g o v / r e s e a r c h / t f h r c /
programs/infrastructure/structures/ltbp/.
S TAT E
HAWAII
Concrete bridges dominate the state’s bridge inventory
by Paul Santo, State of Hawaii Department of Transportation
Kahoma Stream Bridge. All photos: KSF Inc.
T
he first recorded bridge built in Hawaii
was constructed in 1840. The first concrete
bridges in Hawaii’s bridge inventory are recorded
as being built in 1900 and are still in service.
Since then, concrete has been the predominant
construction material for bridges.
More than 85% of the more than 1160 bridges
in the state’s inventory (including the counties)
are constructed with concrete. In the last 50 years,
over 95% of all permanent bridges constructed (not
including culverts) have been made of concrete.
Recent history shows that about nine out of every 10
bridges constructed in Hawaii are made of precast,
pretensioned or post-tensioned concrete elements.
Concrete bridges have proven to be a durable, costeffective solution with lower maintenance concerns
compared to timber and steel bridges.
Hawaii constructed its first bridges using precast,
prestressed concrete girders in 1959. Approximately
30% of the bridges in the state’s inventory are
constructed using pretensioned or post-tensioned
concrete technology. Hawaii’s first concrete
segmental box girder bridge—constructed by the
balanced cantilever method—was the Kipapa
Stream Bridge on Interstate Route H-2 on the island
of Oahu built in 1975.
Recent History
Over the last few years, a number of bridges
with significant innovative applications have been
constructed by the State of Hawaii Department of
Transportation, Highways Division (HDOT).
North-South Road
(Kualakai Parkway) Separation
Completed in 2009, the North-South Road
(Kualakai Parkway) Separation supporting
Interstate Route H-1 on the island of Oahu
provided some innovative developments of highperformance concrete in drilled shafts and
bridge decks. The twin, single-span structures
are each 165 ft long with integral abutments.
Four 5-ft-diameter drilled shafts support each
abutment.
Application of drilled shafts for Hawaii
highway bridges had historically demonstrated
several undesirable concrete properties. The
aggregate usually segregated from the concrete
matrix during placement resulting in lower
density concrete at the top of the drilled shaft. In
addition, data indicated extremely high concrete
temperatures.
To overcome these difficulties, the project
structural engineer designed a cohesive concrete
that did not segregate, remained at temperatures
below 160°F, and displayed temperature
differentials of less than 35°F during hydration.
The mixture proportions, which included
polycarboxylate plasticizers and stabilizers, also
resulted in a flowable concrete with slumps of
about 10 in. This flowable characteristic was
maintained throughout the casting process.
A low cement content (630 lb/yd3) reduced
the hydration temperature. T his wa s
accomplished without much loss of compressive
strength because a low water-cement ratio was
maintained by using a proprietary, synthetic,
air-entraining admixture. Bleed water was
almost non-existent.
The deck concrete materials and proportions
were selected to minimize drying shrinkage,
enhance fatigue endurance, minimize bleeding,
and reduce plastic shrinkage compared with
previous deck mixtures. The concrete contained
a shrinkage-reducing admixture and synthetic
air to improve workability, in combination with
water-reducing, hydration-stabilizing, corrosioninhibiting, and viscosity-modifying admixtures.
For increased durability of the riding surface,
synthetic fibers were added to the deck concrete
to address micro- and macro-cracking. As a
result of the success from this project, a number
of other bridges have subsequently used similar
concrete mixture proportions, especially for the
deck concrete.
Kealakaha Stream Bridge
The Kealakaha Stream Bridge, located on
Hawaii Belt Road (Route 19) on the island
of Hawaii, was featured in the Summer 2010
issue of ASPIRE.TM It is a 720-ft-long, threespan, continuous concrete bridge on an
1800-ft-radius curve with a maximum span of
360 ft. This bridge utilized Washington State
Department of Transportation bulb-tee girders
that were spliced and made continuous with
post-tensioning.
Kealakaha Stream Bridge with existing bridge in background.
Innovative features associated with this
bridge included the use of friction pendulum
seismic isolation bearings and a unique
launching system for the long-span girders.
This bridge is instrumented to monitor its
behavior due to seismic loads as well as other
loading conditions as part of an HDOT research
project being conducted by the University of
Hawaii.
Kahoma Stream Bridge
One of the most unique and innovative
bridges constructed in Hawaii is the Kahoma
Stream Bridge. This bridge is located on the
proposed Honoapiilani Highway (Route
30) realignment on the island of Maui. This
bridge was designed and constructed as part
of a design-build contract. The structure is a
60-ft-wide, 360-ft-long, single span, low-profile,
inverted tied concrete arch bridge on a 1200-ft
radius curve.
Due to the shape of the structure, the top
chord was subjected to tremendous axial
forces, bending moments, and torsion. Thus,
a considerable amount of reinforcing steel was
placed in all top chord components—U-girders,
precast concrete panels above the U-girders,
deck topping, cast-in-place bent caps that
connect the girders, and the top portion of
the end block. Concrete for these components
also required a higher level of attention in the
design, handling of materials, and placement.
For increased durability of the riding surface,
the deck concrete included alkali-resistant
glass and synthetic fibers to address micro- and
macro-cracking. In addition, admixtures were
incorporated to enhance fatigue endurance,
minimize bleeding, increase workability for
proper placement, and reduce plastic shrinkage.
At each abutment, two friction pendulum
bearings were placed to accommodate rotation,
expansion, and contraction of the structure.
After two years of construction at a cost of
about $24 million, the bridge was opened to
motorists in March 2013. As part of an HDOT
research project, the University of Hawaii has
instrumented this bridge and will be monitoring
its behavior.
Lahainaluna Road Separation
and the Kauaula Stream Bridge
Two other bridges on the proposed Honoapiilani
Highway realignment on the island of Maui
are the Lahainaluna Road Separation and the
Kauaula Stream Bridge. Constructed in 2010,
the Lahainaluna Road Separation is an elegant,
slender, 130-ft-long single-span, cast-in-place
post-tensioned concrete, rigid frame bridge with
integral abutments that takes advantage of the
massive basalt rock formations at each abutment.
The Kauaula Stream Bridge, completed
in 2013, is the first geosynthetic reinforced soil
(GRS) integrated bridge system (IBS) constructed
in Hawaii. The 112-ft-long and 47-ft-wide
superstructure is comprised of precast, posttensioned concrete U-girders; precast, stay-in-place
concrete deck panels; and a cast-in-place concrete
deck. The abutments are also skewed at 31 degrees.
This system was proposed by the contractor
as a value engineering proposal in lieu of an
I-girder type superstructure on conventional
type abutments on spread footings. The GRS-IBS
technology provides a cost-effective, accelerated
bridge construction solution.
The GRS abutments have been instrumented
for monitoring as part of an HDOT research
project being conducted by the University of
Hawaii. Funding for the research associated with
this project was provided by the Federal Highway
Administration’s Innovative Bridge Research and
Deployment Program.
Current Practice
The majority of new or replacement bridges in
Hawaii range in span lengths from about 30 to
130 ft. Common practice in the past has been to
use precast, prestressed concrete I-girders with
a composite, cast-in-place concrete deck slab.
Although still used in appropriate conditions,
other structural systems such as adjacent slab
beams (or planks), adjacent U-girders, and
adjacent tee beams with a composite, cast-in-
place, concrete topping are being used to
accelerate bridge construction.
Being an island state, a number of Hawaii’s
highways circle around each island along the
coast in flood prone areas. These alternative
structural systems, especially the adjacent slab
beams or planks, have been effective in providing
increased freeboard for replacement bridges
over waterways. A recommended upper limit for
spans for a precast, prestressed concrete plank
system would be about 60 ft partly because of the
limitation of the precast stressing beds available
in Hawaii. The 80-ft-long, single-span, integral
abutment Kii Stream Replacement Bridge built
in 2005 on the island of Oahu utilized this
system; however, the precast concrete planks
were sequentially post-tensioned rather than
pretensioned to achieve the prestressing.
HDOT’s preference has been to use partialdepth precast concrete deck sections with
composite cast-in-place concrete topping.
The topping provides a means to correct any
differential elevations of the precast concrete
elements due to variations in camber from
prestressing of adjacent elements, superelevation
of roadway, vertical curves, surface imperfections,
and combinations thereof. The reinforced
structural concrete topping also serves as a tie
between the adjacent precast concrete elements,
in addition to the grouted keyways, to make the
units behave as a more cohesive structural system.
Advances in technology of concrete admixtures
have greatly improved the performance and
behavior of concrete. Some of the admixtures
routinely specified for HDOT bridge deck
construction are water-reducing admixtures,
shrinkage-reducing admixtures, water-based
migrating corrosion-inhibitor admixtures, and
polymer-based air-entrainment admixtures.
Other means to enhance concrete performance
of deck slabs include more concrete cover for
top reinforcing steel, use of synthetic fibers, and
specifying maximum shrinkage strains at various
ages of concrete. Also, the use of shrinkagereducing admixtures and corrosion-inhibiting
admixtures are usually specified for other bridge
elements including walls but not for footings and
drilled shafts.
Despite the limited funding available for bridge
construction and maintenance, HDOT’s goal is
to build durable bridges that require minimal
maintenance. The use of concrete has been the
primary means for HDOT.
_________
Paul Santo is bridge design engineer
with the State of Hawaii Department of
Transportation, Highways Division, Bridge
Design Section in Kapolei, Hawaii.
C R E AT I V E C O N C R E T E C O N S T R U C T I O N
Rain Rocks Rock Shed
by Mike Van De Pol, California Department of Transportation
South portal of the Rain Rocks Rock Shed. All photos: California Department of Transportation.
T
he California Department of
Transportation (Caltrans) is making
improvements to Highway 1 along the Big Sur
Coast in Monterey County. The Rain Rocks Rock
Shed project will restore highway reliability,
decrease maintenance expenditures, and
improve safety.
Unstable geology and winter storms cause
landslides and rock fall at the site, regularly
creating significant hardship for travelers and
the coastal communities. Caltrans evaluated
structure types and met with other state
agencies, local agencies, and local community
representatives. Among the alternatives
considered were a bypass structure, a tunnel,
total Highway 1 relocation, and a rock shed.
Multiple rock shed configurations were explored
to meet functional needs and the significant
aesthetic requirements. An aesthetics advisory
committee established goals and guidelines
for the structure relating to form, shape,
proportions, surface textures, and colors.
The selected structure follows the existing
highway alignment and covers the roadway. The
roadway section is composed of two 12-ft-wide
lanes, 4-ft-wide shoulders, concrete barriers, and
steel pipe hand railing. The rock shed is 239.5 ft
long and 54.5 ft wide.
The substructure is composed of two, fivespan, cast-in-place, post-tensioned concrete
arched bent spans. The bent spans are supported
on tapered rectangular concrete columns. The
columns are founded on steel-case, cast-in40 | ASPIRE, Spring 2014
drilled-hole piles with deep rock sockets.
The roof, or superstructure, is composed of
precast, prestressed arched, voided rectangular
concrete girder sections, which rest on the bent
caps. Concrete roof panels are joined together
with post-tensioning in the direction of the
roadway and are affixed to the bent caps with
vertically oriented post-tensioning. The array of
roof panels has a cast-in-place concrete overlay.
Internal and external retaining walls span
between, and are affixed to, the bent span
columns. On each end of the structure, there
are variable height headwalls, intended for
backfill/cover containment, structure hillside
conformance, and visual relief. Tieback anchors
are employed between the structure and the
hillside and between the headwalls. To absorb
rock fall impact loads, a combination of
materials is employed on top of the roof panels.
The roof cover is composed of sand, expanded
polystyrene, coarse aggregate, and a grid system.
The grid system is comprised of a continuous
layer of welded-wire reinforcement (WWR) with
a criss-cross grid of concrete bands that are cast
around the WWR in a specific, normal pattern.
For structural design, a geologic history of
rock fall was obtained. Employing site contours
and computer simulations, rock fall parameters
were developed. Structure impact zones were
established with impact/force equations to
develop rock impact loads on the roof cover.
The impact loads were distributed through the
roof matrix for structural component design.
Multiple staged loadings were evaluated,
including temporary static and construction
equipment live loads.
_______
Mike Van De Pol is a structures designer
for the California Department of
Transportation in Sacramento, Calif.
Interior view of the rock shed with roof panels in place, looking south.
What Certification Program are you betting on?
Certification is more than inspections, paperwork, and
checklists! It must be an integrated and ongoing part of the industry’s
Body of Knowledge! PCI is the technical institute
Phone: 312-786-0300
Fax: 312-621-1114
www.pci.org
Phone: 312-786-0300
Fax: 312-621-1114
www.pci.org
Phone: 312-786-0300
Fax: 312-621-1114
www.pci.org
for the precast concrete structures industry and as such, PCI Certification
is an integrated and ongoing part of the industry’s body of knowledge.
Specify PCI Certification
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To learn more, visit www.pci.org/certification or contact
Dean Frank, P.E., PCI director of quality programs,
at [email protected] or (312) 583-6770.
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U.S. 90 Bridge over Biloxii Bay
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Department of Transportation knew the new 1.6
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a Category 5 hurricane. It also had to include
a 250-foot navigation span, require minimal
maintenance and be constructed quickly. Precast
concrete’s inherent strength, durability, and
speed made it the obvious choice.
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For more information
and free continuing
education, visit
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AUTHORITY
ILLINOIS TOLLWAY
Illinois easily transitions from concrete bridge pioneer to state-of-the-art designs
by Paul Kovacs, Illinois Tollway
T
he Illinois Tollway pioneered the use of
prestressed concrete bridge beams during
construction of the state’s original tollway
system in the late 1950s. Concrete bridge
beams—both standard and unique designs—
continue to be preferred for the tollway’s bridge
structures. Across its 286-mile system of four
interstates in Northern Illinois, the Illinois
Tollway favors the durability and constructability
of concrete bridges, as well as the engineering
advances in the construction techniques for
concrete bridges.
In 2007, the Illinois Tollway completed the
12.5-mile expansion of the Veterans Memorial
Tollway (I-355) featuring the Des Plaines River
Valley Bridge described in the Spring 2008 issue
of ASPIRETM. This bridge spans 1.3 miles over
the Des Plaines River, the Illinois and Michigan
Canal, the Sanitary and Ship Canal, several
railroad lines, and forest preserve land. This was
the first bridge in the state of Illinois to use posttensioned, precast, prestressed concrete bulb-tee
girders.
In 2009, reconstruction of the Reagan
Memorial Tollway (I-88) twin bridges over
the Fox River was completed. Structural
arch members of the twin bridges support a
prestressed concrete beam superstructure to
reflect the design of the original bridges built in
1958. See ASPIRE Summer 2009 for more details.
Today, the Illinois Tollway continues to
lead the way with innovative concrete bridge
designs as part of its 15-year, $12 billion capital
program, Move Illinois: The Illinois Tollway
Driving the Future. Move Illinois will:
• address the remaining needs of the
existing tollway system,
• rebuild and widen the Jane Addams
Memorial Tollway (I-90) as a state-ofthe-art, twenty-first century corridor,
• construct a new interchange to connect
the Tri-State Tollway (I-294) to I-57,
• build a new, all-electronic Elgin-O’Hare
Western Access, and
• fund planning studies for the Illinois
Route 53/120 project and the Illiana
(Illinois-Indiana) Expressway.
Move Illinois will include the reconstruction
of more than 70 mainline and crossroad bridges
as part of the I-90 Rebuilding and Widening
Project. The Elgin-O’Hare Western Access
Project will provide more than 80 new and
improved bridge structures. Shallow depth
beams are being used on the Illinois Tollway
for the first time, and U-shaped girders are
being considered for accelerated construction of
longer spans.
In addition, as part of Move Illinois, the
Illinois Tollway is extending the expected
service life of major bridges out to 100 years.
Reconstruction of the Fox River Bridge on the Reagan
Memorial Tollway (I-88) was completed in 2009. Photo:
Henry G. Russell Inc.
This has prompted the Illinois Tollway to design
several of the mainline bridges along the I-90
corridor with stainless steel reinforcement in
the concrete bridge decks. This is expected to
provide a long-term cost benefit.
Another long-term cost benefit is the
incorporation of integral abutments in bridge
designs. This design feature minimizes the
bridge joints, which have shown to be the
weakest link in the tollway’s bridge performance
chain.
The Illinois Tollway is also adopting the
use of a performance-based deck concrete
specification to reduce shrinkage cracking
that often appears in bridge decks. The Illinois
Tollway’s approach is not to specify how the
mixture proportions are to be developed, but
to specify the end-result requirements for the
plastic and hardened concrete.
Allowing concrete producers to evaluate the
various tools available to reduce deck shrinkage
will enable them to choose the approach that
coincides with the construction contractors’
activities. Options selected by local concrete
producers to achieve the specification
requirements have included shrinkagereducing admixtures and lightweight fines to
provide internal curing.
Fr o m i t s p i o n e e r i n g r o o t s t o t h e
incorporation of state-of-the-art technology,
the Illinois Tollway will continue to incorporate
concrete bridges into its roadway infrastructure.
_______
Traffic on the Des Plaines River Valley Bridge on the Veterans Memorial Tollway (I-355). Photo: Illinois Tollway.
Paul Kovacs is chief engineer for the Illinois
Tollway in Naperville, Ill.
Drava Bridge osijek, Croatia
a combination of rCS and CB climbing
formwork provides an optimal solution.
The internal cantilevered parapets are
suspended on a construction consisting
of VariokiT and Peri UP.
a VariokiT cantilevered parapet
carriage is used to construct the
external cantilevered parapets.
VARIOKIT Construction Kit
Flexible and cost-effective formwork solutions
for every bridge project
Formwork
Shoring
Scaffolding
US Peri 14.063
www.peri-usa.com
CONCRETE CONNECTIONS
Concrete Connections is an annotated list of websites where information is available about concrete bridges. Fast links to the websites
are provided at www.aspirebridge.org.
IN THIS ISSUE
www.michiganhighways.org/indepth/zilwaukee.
html#history
This website contains the history of the Zilwaukee Bridge
described on pages 12 to 14.
performance is currently defined. The report divides bridge
performance into specific issues, identifies the most critical
issues, and describes the types of data necessary to analyze
these issues.
www.wsdot.gov/projects/us97/satuscreekbridge/
Visit this Washington State Department of Transportation
website for additional information about the Satus Creek
Bridge discussed on pages 24 to 26.
NEW www.trb.org/main/blurbs/170201.aspx or
http://onlinepubs.trb.org/onlinepubs/shrp2/
SHRP2prepubR19B.pdf
TRB’s second Strategic Highway Research Program (SHRP
2) Reliability Project R19B has released a prepublication,
non-edited version of a report titled Bridges for Service Life
Beyond 100 Years: Service Limit State Design that explores
design codes critical for bridges to reach a service live of
beyond 100 years. The report also addresses performance
measures and design procedures that utilize criteria to
maximize the actual life of a bridge system.
www.iowadot.gov/MassenaBridge/index.html
Visit this Iowa Department of Transportation website for
information about the Massena Bridge lateral bridge slide
described on pages 33 to 35. The site includes a photo and
video gallery, contract documents, contractor’s submittals,
and a post-construction review.
www.fhwa.dot.gov/research/tfhrc/programs/
infrastructure/structures/ltbp/
This website provides more information about the FHWA
Long-Term Bridge Performance Program summarized in the
FHWA article on pages 36 and 37.
www.pcine.org/index.cfm/projects/bridges
This PCI Northeast website has additional information and
photographs about the Fairmount Bridges described on
pages 20 to 22.
Sustainability
www.sustainableinfrastructure.org
Information about Envision, TM a rating system system for
sustainable infrastructure, is available at this website.
Bridge Technology
www.aspirebridge.org
Previous issues of ASPIRE™ are available as pdf files and
may be downloaded as a full issue or individual articles.
Information is available about subscriptions, advertising, and
sponsors.
www.nationalconcretebridge.org
The National Concrete Bridge Council (NCBC) website provides
information to promote quality in concrete bridge construction
as well as links to the publications of its members.
www.concretebridgeviews.com
This website contains 73 issues of Concrete Bridge Views
(formerly HPC Bridge Views), an electronic newsletter
published jointly by the FHWA and the NCBC to provide
relevant, reliable information on all aspects of concrete in
bridges.
NEW www.fhwa.dot.gov/publications/research/
infrastructure/structures/ltbp/13051/
The FHWA technical report titled LTBP Bridge Performance
Primer is available at this website. The report is intended to
provide a comprehensive definition of bridge performance
that will be the foundation for carefully designed research
studies in the LTBP Program. The report describes the barriers
and complications that hinder the understanding of bridge
performance and identifies the measures by which bridge
NEW http://vimeo.com/83863944
The video on this website highlights the benefits of SHRP
2 ABC Toolkit for using accelerated bridge construction
techniques on standard bridges. It features the replacement
of the I-84 bridge over Dingle Road in New York State.
www.fhwa.dot.gov/research/resources/uhpc.cfm
This FHWA website is the location of considerable
information about ultra-high-performance concrete including
both research and applications.
www.fhwa.dot.gov/publications/research/infrastructure/
structures/hpc/13060
A new report titled Ultra-High Performance Concrete: A
State-of-the-Art Report for the Bridge Community (Pub. No.
FHWA-HRT-13-060) is available at this website. The report
includes information on materials and production, mechanical
properties, and structural design and testing. An extensive list
of references is provided.
www.abc.fiu.edu/wp-content/uploads/2013/07/ABCUser-Guide-for-posting1.pdf
This Florida International University website contains a users’
guide to the National ABC Project Exchange, which is a
nationwide repository of projects that have incorporated
Prefabricated Bridge Elements and Systems (PBES) with other
innovative strategies to accomplish the objects of accelerated
bridge construction.
Bridge Research
www.trb.org/shrp2/researchreports
Are you looking for a research report from the second
Strategic Highway Research Program (SHRP2)? Nearly 90
reports organized by focus area and topic are now available
as free downloads from this website.
http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_
rpt_733.pdf
NCHRP Report 733, High-Performance/High-Strength
Lightweight Concrete for Bridge Girders and Decks presents
proposed changes to the AASHTO LRFD bridge design and
construction specifications to address the use of lightweight
concrete in bridge girders and decks.
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Harbor Drive Pedestrian Bridge | T.Y. Lin International Group
Photo by Brooke Duthie, courtesy of T.Y. Lin International
AASHTO LRFD
Color logos
Repor
t
logos
Reverse
Black only
SD -01-1
Color logos
logos
3
Reverse
logos
Repor
t
State
- of-th
e -Ar
Black only
200 West
Suite 2100
Adams
Street
Phone: Chicago, IL
312-786-0 60606
Fax: 312-621-1 300
www.pci.or 114
g
t on
S eismi
200 West
Suite 2100
Adams
Street
Phone: Chicago, IL
312-786-0 60606
Fax: 312-621-1 300
www.pci.or 114
g
t Rep
or
200 West
Suite 2100
Adams
Street
Phone: Chicago, IL
312-786-0 60606
Fax: 312-621-1 300
www.pci.or 114
g
c Desig
n of
Prec
ete Bridg
es
200 West
Phone: Adams Street
312-786
I Suite
2100
-0300
I Chicago
I Fax:
312-621
, IL 60606-5
-1114
I www.pc 230
i.org
logos
Sta te-
of- the
-Ar t Re
Pre cas Se ism ic Depo rt on
t Co nc
sig
ret e Bri n of
dg es
ast Concr
200 West
Phone: Adams Street
312-786
I Suite
2100
-0300
I Chicago
I Fax:
312-621
, IL 60606-5
-1114
I www.pc 230
i.org
SD
First -01-1 3
Editi
on
TRN14-277
6_Cover.ind
d 1
200 West
Phone: Adams Street
312-786
I Suite
2100
-0300
I Chicago
I Fax:
312-621
, IL 60606-5
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I www.pc 230
i.org
2/21/2014
10:02:25
2014 Interim
Changes Related
to Concrete Structures
by Dr. Dennis R. Mertz
AM
The PCI State-of-the-Art
Report on
Seismic Design of
Precast Concrete
Bridges
Seismic design of precast
concrete bridges begins with
a global analysis of the response of the structure to
earthquake loadings and a
detailed evaluation of connections between precast elements of the superstructure
and substructure. Because
modeling techniques have
not yet been implemented for
jointed details, the focus of
this report is on procedures
for the evaluation of system
response and the detailing
of connections for emulative
behavior.
Seismic analysis procedures
are discussed with the primary emphasis on forcebased analysis procedures.
Displacement-based analysis
and computer modeling are
also discussed. Relevant seismic design criteria of early
years are summarized along
with the current criteria of the
AASHTO Specifications, Caltrans criteria, Japan’s bridge
design, and the New Zealand
Bridge Manual requirements.
This ePubulication is available on line at
http://www/pci.org/epubs
T
he American Association of State Highway
and Transportation Officials (AASHTO)
Subcommittee on Bridges and Structures
(SCOBS) convened their annual meeting
in Portland, Ore., this past June. During the
meeting hosted by the Oregon Department
of Transportation, SCOBS considered and
adopted five agenda items specifically related
to concrete structures. After several years of
development, Technical Committee T-10,
Concrete Design, moved Agenda Items 6, 7, 9,
10, and 11 to subcommittee ballot in Portland.
These agenda items represent revisions and
additions to the AASHTO LRFD Bridge Design
Specifications. This column reviews the 2013
concrete-structures agenda items, which are
integrated into the 2014 seventh edition of the
Specifications.
Agenda Item 6 resolves conflicting
requirements and terminology regarding
the distribution of longitudinal torsion
reinforcement in box girders as specified in
Articles 5.8.3.6.3 and 5.8.6.4. It clarifies that
the calculated value of reinforcement is the
total area of reinforcement to be distributed
around the outer-most webs and top and
bottom slabs of the box girder. The American
Segmental Bridge Institute (ASBI) assisted T-10
in developing this ballot item, although the
provisions in Article 5.8.3 apply to all cellular
concrete cross sections.
The minimum transverse reinforcement
requirement for segmentally constructed posttensioned box girders was unified with that
of all other concrete cross sections of Article
5.8.2.5 in Agenda Item 7. Based upon
new research, this agenda item removes the
previous specified exemption for segmental
post-tensioned boxes and increases the
minimum reinforcement by making it a
function of concrete strength.
Agenda Item 9 addresses a desire to
increase spacing of shear connectors to
facilitate accelerated construction of concrete
bridges with precast concrete deck panels.
It revises Article 5.8.4.2 by increasing the
maximum limit on the spacing of non-welded
shear connectors to 48 in. or the depth of
the member, whichever is smaller. However,
an exception is made for cast-in-place box
girders where the original limit of 24 in. is
maintained. The revisions are based upon the
findings reported in NCHRP Report 584, FullDepth Precast Concrete Bridge Deck Panel
Systems.
Article 5.8.6.5, which specifies the shear
resistance of segmental concrete bridges, is
revised by Agenda Item 10 to allow Article
5.8.3—Sectional Design Model for shear
resistance of concrete members to be applied
to segmental concrete bridges. The traditional
segmental concrete bridge shear-resistance
provisions taken from the AASHTO Guide
Specifications for Design and Construction
of Segmental Concrete Bridges continue to
be an acceptable alternative. This revision
increases the permitted load-carrying capacity
of some segmental bridges; however the
service limit-state check for shear in Article
5.8.5—Principal Stresses in Webs of Segmental
Concrete Bridges, is retained as a check on
serviceability.
Agenda Item 11 primarily clarifies
existing Article 5.10.9.3.4b, regarding crack
control behind intermediate post-tensioning
anchors through tieback reinforcement, with
additional commentary including illustrative
figures. Also, the required length of the tie-back
reinforcement is shortened.
Interim revisions to the AASHTO LRFD
Bridge Design Specifications are considered
annually by SCOBS. Their next meeting is
scheduled for June 22 through 26, 2014, in
Columbus, Ohio.
______________
Dr. Dennis R. Mertz is professor of
civil engineering at the University of
Delaware. Formerly with Modjeski and
Masters Inc. when the LRFD Specifications
were first written, he has continued to be
actively involved in their development.
EDITOR’S NOTE
If you would like to have a specific
provision of the AASHTO LRFD Bridge
Design Specifications explained in this
series of articles, please contact us at
www.aspirebridge.org.
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I-5 over Skagit River Bridge
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Before Repair
THE
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